gms | German Medical Science

Objectives: Lower limb length discrepancy (LLD) is a common source of patient dissatisfaction after total hip arthroplasty (THA). The aim of this study was to assess (i) factors associated with the subjective perception of a postoperative limb length discrepancy, (ii) a LLD cut point when patients tend to percept/complain about LLD, and (iii) which anatomical landmark show the highest agreement between LLD measures and a requested compensation height.

Methods: Ninety-nine patients undergoing unilateral primary THA with a pressfit cementless short stem system were prospectively enrolled. Limb length discrepancy measures where obtained at five different landmarks (acetabular tear drop figure, inferior portion of the sacroiliac joint, superior portion of the sacroiliac joint, iliac crest, and lesser trochanter) preoperatively, at discharge, and 6, 12, 24, and 52 weeks postoperatively. Clinical assessment (Harris Hip Score (HHS) and WOMAC), patient satisfaction, perception of a LLD, and use of a LLD compensation were assessed up to a follow up of 52 weeks.

Results: Intraclass correlation coefficients (ICC) between two independent observer were good to excellent for all LLD measures at various landmarks (95% CI: 0.88 - 0.96). Limb length differences slightly increased within the first 6 postoperative weeks until a steady state was reached. Forthy-three percent of patients reported a perception of a LLD during the first weeks, whereas only 23% a remaining LLD feeling after 52 weeks. A LLD feeling after 52 weeks was associated with a lower satisfaction (p = 0.050), with obvious higher LLD measures (p = 0.043), but not with functional impairments (HHS, p = 0.144; WOMAC, p = 0.109). The cut point for patients reporting a LLD was 9.5 mm measured at the iliac crest (Youden's index = 0.35). Eighty-one percent of patients feeling a LLD (19% in total) requested a LLD compensation. The LLD compensation height (M(SD) = 8.9 (6.5)) remains highly subjective. Limb length discrepancy measures at the iliac crest showed a higher agreement with LLD compensations than other landmarks, but remained insignificant (ICC = 0.49; p = 0.093) with only being able to explain 11% of the amount of variation in LLD compensations.

Conclusion: Limb length discrepancy measures within the first 6 weeks after operation can be biased, as patients tend to not fully straighten or weight-bear during this period. Many patients do feel a LLD directly postoperative, but considerably fewer request a LLD compensation in the long run. Even if patient satisfaction drops with a considerably LLD, the functionality remains high. The decision for a LLD compensation is highly subjective and hardly predictable with anatomical measures.