Factors That Determine Pelvic Obliquity in Adults Who Suffered Legg-Calvé-Perthes Disease and the Role of Total Hip Arthroplasty in Its Restoration.

BACKGROUND

The purpose of the study was to analyze the appearance of pelvic obliquity before total hip arthroplasty (THA) in adults who have Legg-Calvé-Perthes disease (LCPD) sequelae and its evolution in the first two postoperative years, identifying which factors influence its development.

METHODS

The THAs performed between 2012 and 2021 at a single institution in adults who had LCPD during childhood were retrospectively identified. Each case was matched 1:1, based on age at surgery, sex, and body mass index, with a primary THA performed for hip osteoarthritis (OA). A THA was implanted at a mean age of 47 years (range, 21 to 91), and 18 patients (64.3%) were men. We conducted a mean follow-up of 5.1 years (range, two to 10.1). Implant position, soft tissue balance, and pelvic obliquity were evaluated at 6 and 12 weeks and at 1 and 2 years. There were 28 THAs in 25 adults who suffered LCPD, and 28 THAs in patients who underwent surgery due to primary OA were included.

RESULTS

An increase in the initial pelvic obliquity at 6 weeks of THA was observed in both groups (from 3.6 ± 2.8 to 4 ± 3.2 and from 1.3 ± 1.2 to 1.8 ± 1.5, respectively), which progressively decreased at 12 weeks, 1 year, and 2 years after surgery, with final values of 2.2 ± 1.5 and 0.8 ± 0.7 for the LCPD and OA groups, respectively. Only in the LCPD group were the preoperative values associated with a greater limb length discrepancy (Rho = 0.41) and a lower femoral offset (Rho = -0.26) (P < 0.05).

CONCLUSIONS

Patients who suffered LCPD in childhood have greater pelvic obliquity than those who have primary OA, and this is associated with greater limb length discrepancy and less femoral offset. In these patients, THA decreases pelvic obliquity 2 years after its implantation, although it increases in the first weeks, probably due to the shortening of the abductor muscles, so patients should be warned before surgery.

LEVEL OF EVIDENCE: Therapeutic Level IV (Case Series).