Similar to other childhood hip disorders, Legg-Calvé-Perthes disease (LCPD) has the development of degenerative coxarthosis as its natural history. The outcome of this condition is multifactorial, but degenerative changes and subsequent remarkable clinical disability may develop despite adequate comprehensive treatment. According to long-term follow-up studies, most patients are active and pain free for 20 to 40 years after disease onset. However, majority of patients have degenerative changes and marked functional limitations after 40 years.1 Stulberg class V hips are reported to be the worst, usually having significant symptoms by the end of the fourth decade of life.2,3 Therefore, patients with LCPD undergo hip replacement arthroplasty at a relatively young and active age, which is negative for the artificial joint longevity.
For patients with symptomatic degenerative coxarthrosis secondary to LCPD that is not managed with adequate conservative treatment, hip replacement arthroplasty is the last, but a very reliable and effective therapeutic modality. However, this is a relatively uncommon (0.7% to 3%) indication for hip replacement arthroplasty,4–6 and there have been no studies specifically addressing total hip arthroplasty (THA) for this population.
Patients with late-stage LCPD frequently have various deformities of the proximal femur and acetabulum caused by the disease itself and by surgical treatments. Owing to these deformities and/or retained hardware, a standard THA can be a complicated procedure. However, it seems that the resulting technical difficulties are not severe enough to cause less favorable prognosis of THA in patients with LCPD than in patients with other disease. It might be a reason for the rarity of the reported studies about THA in patients with LCPD. It is quite contrary to the developmental dysplasia of the hip (DDH). There have been a large number of studies focusing on the surgical problems, optimal techniques, and follow-up results for THA in patients with DDH. Most arthroplasty textbooks allocate a separate section to DDH, but not to LCPD.
SKELETAL DEFORMITIES CAUSED BY DISEASE ITSELF
Coxa breva, a typical residual deformity of LCPD, consists of a short femoral neck, a large oval-shaped femoral head, a relatively overgrown greater trochanter, and a decreased femoral neck-shaft angle. The acetabulum is also deformed to be flat, losing its concavity to accommodate the deformed femoral head. Frequently, femoral head is subluxated laterally and covered by the acetabulum incompletely (Fig. 1A).
In contrast to the markedly deformed head and neck area, no significant deformity develops distally in the intertrochanteric area and diaphysis. Therefore, there is no remarkable difficulty in implanting ordinary femoral stems. A shortened limb length can be restored without difficulty because the shortening is usually less than 3 cm (Fig. 1B).
One technical point worth noting is that neck cutting should be performed in the middle of the femoral head in cases in which the femoral head and neck deformities are severe. As the femoral neck is short and covered by a mushroom-shaped femoral head, neck cutting at the lower margin of the exposed femoral head results in complete removal of the femoral neck frequently with some portion of the lesser trochanter (Fig. 2).
The acetabulum is flat and sometimes dysplastic relatively. However, the medial wall is usually sufficiently thick for stable fixation of the acetabular cup without ancillary procedures (Fig. 1A). One minor technical point is to start acetabular reaming with a reamer much smaller than the exposed acetabular surface. As the enlarged acetabulum is relatively shallow, there is a risk of overreaming if the reaming is started with a reamer fit to the exposed acetabular surface, especially when there is a degenerative spur formed along the margin of the acetabulum (Fig. 1B).
SKELETAL DEFORMITIES SECONDARY TO SURGICAL TREATMENTS
Bony procedures for LCPD include pelvic and proximal femoral osteotomies to achieve good containment of the femoral head, valgus femoral osteotomy for hinged abduction, and greater trochanteric transfer to improve the abductor mechanism.7
Pelvic osteotomies usually make the acetabular shape better for cup fixation, and proximal femoral osteotomies usually leave no significant deformities, which would make THA difficult to perform. These procedures are usually performed during the growth phase; thus, the osteotomy sites have sufficient time to remodel (Fig. 3).
Greater trochanteric transfer can make a THA difficult when there is significant limb shortening. When limb length is restored by a THA, the greater trochanter is located too distal and must be relocated with an osteotomy to avoid excessive abductor tension.
PROGNOSIS OF THA
The LCPD patient group has well-known negative prognostic factors for THA, such as young age and male sex. Therefore, a less favorable prognosis might be expected in patients with LCPD. There were 2 large outcome studies from the Norwegian arthroplasty register4 and the Danish hip arthroplasty registry,6 respectively. Both reported no differences in outcome between the LCPD group and primary arthritis group.
RESURFACING FOR LCPD
Resurfacing arthroplasty is an alternative to conventional THA, especially for young patients. It has the advantages of preservation of the proximal femur, wider range of motion, and low wear rate of its metal-on-metal bearing surface. Resurfacing can be a good option for patients with LCPD who undergo replacement arthroplasty at a relatively young age. Theoretically, it has the added advantage of no necessity to address the proximal femoral deformities in this patient group. However, natural deformity of the short and wide femoral neck makes resurfacing difficult or impossible in patients with LCPD. Owing to the low head-to-neck ratio, it is difficult to ream the femoral head without making a notch in the femoral neck, which is known to be an important cause of early failure (Fig. 4).8 It is difficult to gain leg length, and the high greater trochanter causes impingement.5,9 Leg length can be gained by inserting more cement between the prepared femoral head and the femoral implant (Fig. 5). However, thick cement mantle is also known to be a possible cause of early failure.8,10 Not all, but some LCPD cases are suitable for resurfacing arthroplasty (Fig. 6).
Some surgeons have reported encouraging short-term results of resurfacing in patients with LCPD.5,9 They used greater trochanteric transfer to avoid impingement when necessary, but the limb length restoration was inadequate.
Natural and iatrogenic deformities of LCPD can make THA difficult, but the resulting difficulties are not significant enough to cause poor long-term results. Even though the LCPD patient group has known negative prognostic factors (young age and male sex), its THA results have been reported to be comparable with that of the primary coxarthrosis group.
Resurfacing arthroplasty is technically difficult or impossible in patients with LCPD because of the short and wide femoral neck. There have been a very limited number of reports and the short-term results were satisfactory. When it is performed in selective cases with or without greater trochanteric transfer, satisfactory results are expected; however, long-term follow-up studies are necessary.
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