CLINICO-RADIOLOGICAL EVALUATION OF LEGG-CALVE-PERTHES DISEASE MANAGED BY PROXIMAL FEMORAL VARUS DEROTATION OSTEOTOMY: A RETROSPECTIVE STUDY

Legg-Calve-Perthes disease is a juvenile idiopathic aseptic and non-inflammatory osteonecrosis of immature hip. It is associated with both substantial hip pain and dysfunction during the disease process as well as later in adulthood. The goals of treatment are to decrease pain, reduce the loss of hip motion, and prevent or minimize permanent femoral head deformity. Children with Perthes disease, of both genders were managed by proximal femoral varus derotation osteotomy. Evaluation was done in terms of; clinical symptoms and signs, Harris hip score, and radiologically with X-rays. The results indicated improvement in pain, limp, abduction, internal rotation and Harris Hip Score which was statistically significant. In conclusion, proximal femoral varus derotation osteotomy is an acceptable method for management of patients with Legg-Calve-Perthes disease. This surgery led to decrease in pain, limping, and an increase in range of motion.


Introduction
egg-Calve-Perthes disease (LCPD) is a juvenile idiopathic aseptic, noninflammatory, immature hip osteonecrosis in which femoral epiphysis blood supply is not adequate and the bone dies temporarily, followed by subchondral fracturing, fragmentation, revascularization and remodeling. Both severe hip pain and dysfunction during the disease phase and later in adulthood are associated with it. Vascular occlusion is reversible, with complete epiphysis revascularization occurring over a span of 2-4 years if the child is under 12 years of age at the onset of the disease. Legg-Calve-Perthes disease predominantly occurs in boys between the ages of 4 and 8 and has been associated with socioeconomic disadvantage in a number of small hospital-based studies [1][2][3] . If treatment is not initiated early in the disease process, eventual flattening and subluxation of the hip joint occurs. It is a major precipitant of premature osteoarthritis of the hip and frequently necessitates hip replacement in early adulthood 4,5 . It is one of the most common, but most poorly understood disorders encountered by pediatric orthopedic surgeons. Incidence rates vary considerably between countries though there is also significant variation within countries and even within regions. Many children, especially those until age 6, the initiation of the disease is clearly asked to refrain from contact sports or games that affect the hip. The best care choice remains unknown for older children (onset of Perthes after age 6). Prolonged periods of non-weight bearing, osteotomy (femoral or pelvic) and the form of hip distraction using an external fixator are current treatment options for older children above 8 years of age. The aims of therapy are to alleviate discomfort, to decrease hip mobility loss and to prevent or minimize permanent femoral head deformity, so that the risk of developing adult extreme degenerative arthritis can be minimized. To assess risks and treatment options, assessment by a pediatric orthopedic surgeon is recommended. Younger kids get a better prognosis than older kids. Surgical containment has become widely accepted as the best method for treating Legg-Calve-Perthes disease 6 . Containment treatment is designed to center the femoral head within the acetabulum during the period of "biologic plasticity". This helps the acetabulum during the healing process to act as a mold 7 . Either proximal femoral varus derotation osteotomy or Salter innominate osteotomy have been the most popular methods for surgical containment 8,9 . Any of these methods can provide sufficient control for mild to moderate LCPD, but in more extreme cases, they may be problematic. About 70-90 percent satisfactory results were reported by advocates of proximal femoral varus derotation osteotomy [10][11][12][13] . The aim of this study is to analyze the clinico-radiological evaluation of Legg-Calve-Perthes disease managed by Proximal Femoral Varus Derotation Osteotomy.

Patients & methods
This open ended cohort study was conducted over a period of one year, on patients diagnosed clinically and radiologically as Perthes disease and operated upon between 2012 to 2017, presenting at the outdoor department of Pediatric Orthopedic Surgery, King George's Medical University, Lucknow, India. All the children (up to 16 years) presenting with Perthes disease, of either sex and willing to get enrolled in the study and were managed by proximal femoral varus derotation osteotomy were included in the study. We excluded the patients if they had any other cause of avascular necrosis of femoral head, like post traumatic, post infective; patient presenting with blood dyscrasias like hemophilia, sickle cell disease; patient on steroids, subjects with associated neuromuscular disorder, associated congenital deformity of lower limb, and patients with metabolic diseases such as Rickets. The assessment tools used in this study were; history, clinical examination for pain, Trendelenburg gait, range of motion and shortening, Harris hip score, X-ray, MRI and statistical analysis of the data collected. Patient was placed in supine on the operating table and lateral approach taken for exposure. The level of the osteotomy marked at the level of the lesser trochanter or slightly distal with image intensifier. Subtrochanteric osteotomy is done by oscillating saw and the fragments are fixed with a pre-bent plate (3.5 mm Dynamic Compression Plate) to ensure a varus angulation of 20 degree done at an aim to achieve the neck shaft angle of 110-115 degree to confirm the femoral head centered concentrically in the acetabulum. Epiphyseodesis of the greater trochanter is done to prevent relative trochanter overgrowth by inserting one screw through the greater trochanter. Irrigate the wound and close in layers, insert a suction drain if needed. Stitches are removed on 12th postoperative day. Follow-up is done at 4 weeks interval till 3 months. Non weight bearing for 8-10 weeks until union occurs. After 3 months, follow-up done at 12 weeks interval with relevant shoe raise, in patients complaining of limping. Implant removal done after 2 years.

Results
In the current study a total of 19 patients were included out of which 14 (73.68%) were males and 5 (26.32%) were females. The mean duration of follow-up was 51.67±6.95 months. Amongst the study population, 73.68% (14/19) patients underwent surgery at age between 6-10 years. None of the patients had surgery at less than 6 years and 26.32% (5/19) had surgery at the age more than 10 years. There was almost an equal incidence of laterality, with right sided involvement being seen in 47.37% (9/19) (9/19) patients at final follow-up which was found to be highly significant (p=0.001). On comparing the pre-operative and final follow-up range of abduction in the patients it was found that the preoperatively mean abduction was 18.47±4.03 degree which improved to 28.68±5.97 degree at the final follow-up, which was an improvement of 10.21±5.10 degree. According to Paired t-Test this increase in abduction was highly significant (p<0.001). On comparing the pre-operative and final follow-up range of internal rotation movement in the patients, it was found that preoperative mean internal rotation was 11.84±5.82 degree which increased at the final follow-up to 30.32±7.79 degree. So a change of 18.48±6.88 degree was seen which was highly significant (p<0.001) ( Table I).  (Table II).  Harris hip score was excellent in 10.5% (n=2) cases, fair in 26.3% (n=5) cases, good in 63.2% (n=12) case and poor in 0% cases (Figures 1 & 2).

Discussion
The aim of this study was to evaluate the clinico-radiological outcome of proximal femoral varus derotation osteotomy in Perthes disease in retrospectively studied patients. The decision to treat LCPD surgically is influenced by factors like; age of onset of the disease, extent of involvement of the femoral capital epiphysis, and radiographic signs [14][15][16][17][18] . Containment of the femoral head within the acetabulum is currently the preferred method of treatment which can be achieved by either non-operative or operative methods 19 . Initial surgical containment methods concentrated on containing the femoral head within the acetabulum by proximal femoral varus derotation osteotomy 20,21 . Proximal femoral varus derotation osteotomy is a familiar procedure and it offers adequate coverage of femoral head within the acetabulum. It also decompresses the hip joint due to its femoral shortening effect. The disadvantages are limb shortening with prolonged abductor limp and possibility of persistent varus leading to trochanteric prominence. Advantage of osteotomy is that the duration of the disease can be shortened and it can bypass the stage of fragmentation to attain the regeneration phase. Subtrochanteric osteotomy also stimulates retinacular revascularization as it augments blood flow to the femoral head and acetabulum through hypervascularization effect. We in this study, have managed all the cases of Perthes disease with age more than 6 years by proximal femoral varus derotation osteotomy. Our study results are consistent with the findings of B. Joseph et al in which the author had concluded that, the short-term results of early surgical containment in children over seven years of age are satisfactory.
In our study the final functional outcome as assessed by Harris hip score was statistically significant as compared to the preoperative status 22 . Raghav Saini et al in their prospective cohort study concluded that surgical intervention (proximal femoral varus derotation osteotomy) in children with severe Perthes disease, especially who are younger than 10 years of age has a good clinico-radiological outcome and is an effective and easy surgical containment method 23 . They further concluded that patients with a higher degree of involvement (Herring C) tend to have greater femoral head collapse, more pronounced femoral head and neck deformities, greater restriction of the range of motion of the hip and poor prognosis [24][25][26] . We in our study also favor the surgical containment in LCPD by proximal femoral varus derotation osteotomy as we have operated on all the cases (older than 6 years of age with Herring grade A, B or C) of either gender with good functional outcome as assessed by Harris hip score. Our study findings of good functional outcomes in Perthes disease cases managed by proximal femoral varus derotation osteotomy are consistent with the findings of C. J. Coates et al who had excellent clinical functions in all their cases managed by proximal femoral varus derotation osteotomy as assessed by Harris and Iowa scores except those cases who were managed at less than five years of age 27 . We had no patient in our study that got operated at less than 6 years age.
According to M. H. Moghadam et al study, proximal femoral varus derotation osteotomy is an appropriate method for treating Legg-Calve-Perthes disease patients. The outcome of this surgery was a reduction in pain, limping, and an improvement in range of motion 28 . We have also concluded in our study that there is a significant improvement in the range of motion, especially abduction and internal rotation. We in our study have considered Herring classification as a radiological parameter for assessment of LCPD which shows no significant difference between preoperative and final follow-up visits in both the groups. A. Arkader et al in their study has also similar observations but on the modified Stulberg criteria 29 . This may be due to the reason that the follow-up was short. In our study, we favor proximal femoral varus derotation osteotomy as preferred surgical intervention in patients of age more than 6 years of either gender as it results in better functional outcome with decreased morbidity as compared to conservatively managed cases as were evidenced in the literature. Conclusion: According to our study, proximal femoral varus derotation osteotomy is an acceptable method for management of patients more than 6 years with Legg-Calve-Perthes disease. This surgery led to decrease in pain and Trendelenburg gait, increase in range of motion, and improvement in Harris hip score by giving a congruent hip.