Relationship between perceived and structural leg length discrepancies of patients with hip osteoarthritis dysplasia

Only few studies have been conducted on leg length discrepancy (LLD) in patients with hip osteoarthritis (OA). This study aimed to examine the relationship between perceived LLD (pLLD) and structural LLD (sLLD) in patients with advanced OA and to determine the factors influencing both LLDs. This retrospective study aimed to answer the following questions: (1) are older adults less likely to perceive LLD than younger adults? (2) is there a relationship between pLLD and sLLD? and (3) is pLLD associated with patient satisfaction?

We hypothesized that older adults are less likely to perceive LLD than younger adults.

We recruited 125 patients (102 women and 23 men) with hip OA associated with developmental dysplasia of the hip defined as grade 3 or higher according to the Tönnis classification and excluding contralateral grade 2 or higher. The mean age of the patients was 65.2±11.2 (36-85) years. Before surgery, 2-mm and 5-mm thick plates were placed on the floor on the plantar surface of the short leg to measure pLLD. Preoperative computed tomography (CT) was performed and sLLDs were measured using the 3D planning software ZedHip. The following associated factors were evaluated: age, height, weight, body mass index (BMI), adduction and abduction range of motion (ROM) of the affected hip joint, Crowe classification, standing pelvic inclination in the coronal plane, Cobb angle and Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ).

The absolute difference between pLLD and sLLD was modestly positively correlated with age (R=0.206; p<0.05) indicating older patients were less prone to perceive LLD. A strong positive correlation was found between pLLD (4.8±7.3mm; range: -37 to 28mm) and sLLD (6.4±7.0mm; range: -29.9 to 23.7mm) (R=0.714, p<0.05). The greater the pLLD, the smaller the hip abduction ROM (24.8±11.6°; range: 0 to 45°) tended to be, while the greater the sLLD, the smaller the hip abduction and adduction ROM (10.3±5.7°; range: 0 to 25°) tended to be (R= -0.259 and R= -0.297, respectively; p<0.05) The clinical significance of this finding is that pLLD may be improved if hip ROM training is performed before surgery. pLLD was significantly smaller in the group without pelvic inclination (8.0±14.1mm; range: -37 to 22mm) than in the group with pelvic inclination to the affected side (6.9±7.5mm; range: -12 to 28mm) and in the group with no inclination to the affected side (7.3±7.6mm; range: -8 to 25mm) (p<0.05) The clinical significance of this finding is that improving pelvic inclination with hip ROM training or muscle stretching may also reduce pLLD. No significant differences were noted between pLLD and JHEQ total scores or subgroups.

Older patients had less pLLD. Preoperative pLLD was strongly correlated with sLLD but not with patient satisfaction. These results may be useful for conservative treatment of OA, preoperative planning and intraoperative leg length correction.

IV; case control study.