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Bone & Joint Research
Vol. 12, Issue 9 | Pages 571 - 579
20 Sep 2023
Defining the optimal position of the lipped liner in combination with cup orientation and stem version
Navacchia A Pagkalos J Davis ET
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Aims

The aim of this study was to identify the optimal lip position for total hip arthroplasties (THAs) using a lipped liner. There is a lack of consensus on the optimal position, with substantial variability in surgeon practice.

Methods

A model of a THA was developed using a 20° lipped liner. Kinematic analyses included a physiological range of motion (ROM) analysis and a provocative dislocation manoeuvre analysis. ROM prior to impingement was calculated and, in impingement scenarios, the travel distance prior to dislocation was assessed. The combinations analyzed included nine cup positions (inclination 30-40-50°, anteversion 5-15-25°), three stem positions (anteversion 0-15-30°), and five lip orientations (right hip 7 to 11 o’clock).

The Bone & Joint Journal
Vol. 103-B, Issue 9 | Pages 1479 - 1487
1 Sep 2021
Using an asymmetric crosslinked polyethylene liner in primary total hip arthroplasty is associated with a lower risk of revision surgery
Davis ET Pagkalos J Kopjar B
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Aims

The aim of our study was to investigate the effect of asymmetric crosslinked polyethylene liner use on the risk of revision of cementless and hybrid total hip arthroplasties (THAs).

Methods

We undertook a registry study combining the National Joint Registry dataset with polyethylene manufacturing characteristics as supplied by the manufacturers. The primary endpoint was revision for any reason. We performed further analyses on other reasons including instability, aseptic loosening, wear, and liner dissociation. The primary analytic approach was Cox proportional hazard regression.

Bone & Joint Research
Vol. 9, Issue 9 | Pages 563 - 571
5 Sep 2020
A higher degree of polyethylene irradiation is associated with a reduced risk of revision for aseptic loosening in total hip arthroplasties using cemented acetabular components
Davis ET Pagkalos J Kopjar B
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Aims

To investigate the effect of polyethylene manufacturing characteristics and irradiation dose on the survival of cemented and reverse hybrid total hip arthroplasties (THAs).

Methods

In this registry study, data from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man (NJR) were linked with manufacturing data supplied by manufacturers. The primary endpoint was revision of any component. Cox proportional hazard regression was a primary analytic approach adjusting for competing risk of death, patient characteristics, head composition, and stem fixation.

The Bone & Joint Journal
Vol. 102-B, Issue 1 | Pages 90 - 101
1 Jan 2020
Polyethylene manufacturing characteristics have a major effect on the risk of revision surgery in cementless and hybrid total hip arthroplasties
Davis ET Pagkalos J Kopjar B
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Aims

The aim of this study was to identify the effect of the manufacturing characteristics of polyethylene acetabular liners on the survival of cementless and hybrid total hip arthroplasty (THA).

Methods

Prospective cohort study using linked National Joint Registry (NJR) and manufacturer data. The primary endpoint was revision for aseptic loosening. Cox proportional hazard regression was the primary analytical approach. Manufacturing variables included resin type, crosslinking radiation dose, terminal sterilization method, terminal sterilization radiation dose, stabilization treatment, total radiation dose, packaging, and face asymmetry. Total radiation dose was further divided into G1 (no radiation), G2 (> 0 Mrad to < 5 Mrad), G3 (≥ 5 Mrad to < 10 Mrad), and G4 (≥ 10 Mrad).

Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_III | Pages 255 - 255
1 Jul 2011
56. COMPUTER NAVIGATED HIP RESURFACING: AN EVALUATION OF ACCURACY AND LEARNING CURVE
Olsen M Davis ET Waddell JP Schemitsch EH
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Purpose: Hip resurfacing is a technically demanding alternative to total hip arthroplasty. Placement of the initial femoral guidewire utilizing traditional mechanical jigs may lead to preparatory errors and a high degree of variability in final implant stem-shaft angle (SSA). Intraoperative computer navigation has the potential to decrease preparatory errors and provide a reliable method of femoral component placement. The current study evaluated the accuracy and learning curve of 140 consecutive navigated hip resurfacing arthroplasties.

Method: Between October 2005 and May 2007, 140 consecutive Birmingham Hip Resurfacings were performed on 132 patients (107 male, 25 female). The mean age of the cohort was 51.2 years (range 25–82). Indications for surgery included osteoarthritis (n=136) and avascular necrosis (n=4). Preoperative templating was performed using digital AP unilateral hip radiographs. Neck-shaft angles (NSA) were digitally measured and relative implant stem-shaft angles planned. The central guidewire was drilled and verified intra-operatively using an imageless navigation system. Implant stem-shaft angles were assessed using 3 month post-operative radiographs.

Results: Pre-operative templating determined a mean NSA of 132.2 degrees (SD 5.3 degrees, range 115–160). The planned SSA was a relative valgus alignment of 9.5 degrees (SD 2.6 degrees). The post-operative SSA differed from the planned SSA by 2.5 degrees (SD 1.9 degrees, range 0–8). The final SSA measured within ±5 degrees of the planned SSA in 89% of cases. Of the remaining 11% of cases, all measurements erred in valgus. No cases of neck notching or varus implant alignment occurred in the series. The mean navigation time for the entire series was 18 minutes (SD 6.6 minutes, range 10–50). A learning curve was observed with respect to navigation time, with a significant decrease in navigation time between the first 20 cases and the remainder of the series. There was no evidence of a learning curve for implant placement accuracy.

Conclusion: Imageless computer navigation shows promise in optimizing preparation of the femoral head and reducing the introduction of mechanical preparatory factors that predispose to femoral neck fracture. Navigation may afford the surgeon an accurate and reliable method of femoral component placement with negligible learning curve.