Inaccurate offset restoration in total hip arthroplasty results in reduced range of motion

Abstract

Offset restoration in total hip arthroplasty (THA) is associated with postoperative range of motion (ROM) and gait kinematics. We aimed to research into the impact of high offset (HO) and standard stems on postoperative ROM. 121 patients received cementless THA through a minimally-invasive anterolateral approach. A 360° hip ROM analysis software calculated impingement-free hip movement based on postoperative 3D-CTs compared to ROM values necessary for activities of daily living (ADL). The same model was then run a second time after changing the stem geometry between standard and HO configuration with the implants in the same position. HO stems showed higher ROM for all directions between 4.6 and 8.9° (p < 0.001) compared with standard stems but with high interindividual variability. In the subgroup with HO stems for intraoperative offset restoration, the increase in ROM was even higher for all ROM directions with values between 6.1 and 14.4° (p < 0.001) compared to offset underrestoration with standard stems. Avoiding offset underrestoration resulted in a higher amount of patients of over 20% for each ROM direction that fulfilled the criteria for ADL (p < 0.001). In contrast, in patients with standard stems for offset restoration ROM did increase but not clinically relevant by offset overcorrection for all directions between 3.1 and 6.1° (p < 0.001). Offset overcorrection by replacing standard with HO stems improved ROM for ADL in a low number of patients below 10% (p > 0.03). Patient-individual restoration of offset is crucial for free ROM in THA. Both over and underrestoration of offset should be avoided. Although total hip arthroplasty (THA) is a highly successful treatment option for end-stage osteoarthritis with a positive responder rate of over 90% 1, the surgeon is faced with high patients' expectations regarding the functional capacity of the artificial hip joint. Beside a correct intraoperative orientation of both cup and stem, restoration of biomechanics such as offset is crucial for optimal function and long-term outcome after THA 2-4. Failure of correct offset restoration is associated with impingement, reduced hip abductor strength, altered gait kinematics and even higher wear of the artificial hip joint 5-8. To address the interindividual variability of the femoral anatomy, most modern implant systems offer at least two different offset geometries of the femoral stem-a standard offset design and a high offset design 9. Prior to surgery the biomechanical restoration of offset is usually templated on radiographs illustrating the preferred stem design for the respective patient. However, intraoperative alterations in relation to the preoperative plan or reduced joint stability harbour the potential to complicate the right choice of femoral offset design during THA. The discussion of correlation between high offset (HO) stems and higher range of motion (ROM) is controversial in literature. Although aiming to find the balance between the risks of impingement due to offset reduction on the one hand and po...

Robotic-assisted versus manual total hip arthroplasty in obese patients: a retrospective case–control study

“…Inaccurate center of rotation (COR) restoration is associated with impingement, reduced hip abductor strength, altered gait kinematics, reduced postoperative hip range of motion, trochanteric pain, instability, and higher rates of wear [19,[27][28][29]. The horizontal distance of the COR is also considered as the acetabular offset.…”

Analysis of the Risk of Wear on Cemented and Uncemented Polyethylene Liners According to Different Variables in Hip Arthroplasty

“…This has important clinical implications. Using this type of stem could prevent the risk of dislocation in high-risk patients [ 35 ], and these stems are an essential option for restoring biomechanics and enabling a free range of motion without impinging on the activities of daily living in a substantial proportion of patients [ 36 ].…”

Optimal combined anteversion range for obtaining a wider range of motion without prosthetic impingement after total hip arthroplasty: a three-dimensional analysis study

“…Moreover, the prosthetic ROM in those directions was measured using a previously reported method [ 9 ]. Several reports have shown that the ROM was affected by the femoral offset and head diameter [ 10 – 13 ]; therefore, in all cases, the femoral offset was standardized to a stem with a standard offset type and the minimum neck length for each stem. The femoral head diameter was standardized to 32 mm, and the prosthetic ROM was measured.…”