Joint Perception After Total Hip Arthroplasty and the Forgotten Joint

Area of Science:

• Orthopedics and Sports Medicine
• Rehabilitation and Physical Therapy

Background:

• Traditional scoring systems for total hip arthroplasty (THA) functional outcomes are limited by ceiling effects, hindering precise assessment.
• The Forgotten Joint Score (FJS) is proposed as a more sensitive measure, but the specific score defining a "forgotten joint" remains undefined.
• The Patient's Joint Perception (PJP) question was developed to capture patient perspectives on their prosthetic joint, addressing the concept of joint perception.

Purpose of the Study:

• To define the score threshold for a "forgotten joint" using the FJS.
• To evaluate the correlation between the FJS, the Patient's Joint Perception (PJP) question, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
• To assess the ceiling effects of the FJS and WOMAC in patients following THA.

Main Methods:

• A cohort of 257 total hip arthroplasties was evaluated at a mean follow-up of 68 months.
• Functional outcomes were assessed using the WOMAC, FJS, and the newly developed PJP question.
• Statistical analyses included correlation of scores (Spearman's rho) and evaluation of ceiling effects.

Main Results:

• The mean FJS was 88.5, with 52% of patients reporting a natural hip sensation (FJS 93.3-96.0).
• Both WOMAC and FJS exhibited high ceiling effects (27.2% and 31.9%, respectively).
• A significant proportion of patients achieved maximum scores on WOMAC or FJS yet did not perceive their hip as natural, highlighting limitations of these scales.

Conclusions:

• A "forgotten hip" perception is defined as an FJS score greater than 93.
• The WOMAC and FJS failed to identify a "forgotten joint" in 20%-30% of cases, indicating limitations in capturing natural joint perception.
• The PJP question is a simple, reliable tool for identifying patients who perceive their prosthetic hip as natural.