Accuracy of leg length and femoral offset restoration after total hip arthroplasty with the utilisation of an intraoperative calibration gauge

Abstract

Background: Offset and leg length (LL) restoration are critical for the achievement of a stable, well-functioning hip following total hip arthroplasty (THA). Several techniques are described in the literature, including a hip calibration gauge. We question whether meticulous preoperative planning of a specific surgical technique in combination with the utilisation of a calibration gauge can provide an accurate offset and LL restoration. Methods: Retrospective review of 101 unilateral THAs via a posterior approach by a single surgeon. Preoperative radiographic LL and offset were radiographically calculated. Intraoperatively prior to hip dislocation a calibration gauge was used to measure LL and offset with a pin inserted into the iliac crest acting as a static referencing point. All had pelvis x-ray performed 6 weeks postoperatively. A literature review was conducted to establish average postoperative LL/offset values for statistical comparison. Results: The average absolute postoperative leg-length discrepancy (LLD) was 2.51 mm compared to preoperatively 3.54 mm ( p = 0.018). A total of 93.1% and 100% had LLD of ⩽5 mm and ⩽10 mm, respectively. The mean postoperative offset difference was 2.39 mm. The investigated LLD and offset results were comparable with literature data of studies utilising an intraoperative measuring device. LLD was significantly decreased when compared to a free-hand technique (LLD 4.42 mm, p < 0.001). Conclusion: The technique utilising preoperative templating, intraoperative offset verification together with the use of hip calibration gauge yielded accurate LLD and offset restoration as in the literature. Precise offset restoration, which often is a neglected issue, can lead to better abductor vector restoration, hip function and less pain.

Leg Length and Offset After Total Hip Arthroplasty: The Intraoperative use of a Calliper Improves the Results. Should Component Subsidence Influence the Target for Leg Length?

“…In agreement with Barbier et al, the calliper seems to better predict the leg length than the offset [12]. Our study also con rms that good results using the calliper can be achieved with other surgical approaches as we used a different approach than Barbier et al or Enke et al [10,12].…”

“…The nal results on LLD of our patients post THA on the post-OP x-ray are comparable to the results of other studies using a CAL intraoperatively [10,12]. There also is a good correlation of the intraoperative measurements of the leg length and total offset using the calliper in reference to the values measured on the antero-posterior x-ray of the pelvis.…”

“…There also is a good correlation of the intraoperative measurements of the leg length and total offset using the calliper in reference to the values measured on the antero-posterior x-ray of the pelvis. As shown in the literature, the use of a calliper intraoperatively signi cantly improves the results on leg length and offset in comparison to just using clinical tests or templating [10,11,12]. Similarly with all other studies, we also considered the following targets: no leg length discrepancy and the restoration of the offset on the x-ray pelvis taken postoperatively.…”

“…There are different CALs on the market, using the same principle with a xed reference point on the pelvis and a mobile point on the femur [6,10]. They all are similar and function successfully.…”

Letter to the Editor, “Who Restores Hip Biomechanics More Effectively After a Femoral Neck Fracture? Comparison of Total Hip Arthroplasties Performed by Either Hip Surgeons or Orthopedic Residents”

“…Leg length has been shown to play a role in hip stability as well as patient satisfaction postoperatively [4,5] and is more difficult to accurately restore when total hip arthroplasty is performed for fractures vs osteoarthritis such that this research is meaningful and informative. Measuring leg length and femoral offset for hip arthroplasty is challenging on plain film imaging as hip rotation and flexion can influence the landmarks leading to platforms and algorithms designed to capture this intraoperatively [6][7][8][9].…”