Advertisement for orthosearch.org.uk
Results 1 - 7 of 7
Results per page:
Applied filters
Content I can access

Include Proceedings
Dates
Year From

Year To
Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_14 | Pages 7 - 7
1 Nov 2021
Morlock M Bätz J Beverland D Board T Lampe F Konow T
Full Access

The influence of the surgical process on implant loosening and periprosthetic fractures (PPF) as major complications in uncemented total hip arthroplasty (THA) have rarely been studied due to the difficult quantification. Meanwhile registry analyses have clearly shown a decrease in complications with increasing experience. The goal of this study was to determine the extent of variability in THA stem implantation between highly experienced surgeons with respect to implant-size, -position, press-fit, contact area, primary stability and the effect of using a powered impaction tool.

Primary hip stems were implanted in 16 cadaveric femur pairs by three experienced surgeons using manual and powered impaction. Quantitative CTs were taken before and after each process step and stem tilt, canal-fill-ratio, pressfit and contact area between bone and implant determined. 11 femur pairs were additionally tested for primary stability under cyclic loading conditions.

Higher variations in press-fit and contact area between the surgeons for manual impactions compared to powered were observed. Stem tilt and implant sizing varied between surgeons but not between impaction methods. Larger stems exhibited less micromotion compared to smaller stems.

Larger implants may increase PPF risk, while smaller implants reduce primary stability. The reduced variation for powered impactions indicates that appropriate measures may promote a more standardized process. The observed variations between the experienced surgeons may represent the acceptable range for this specific stem design. Variability in the implantation process warrants further investigations since certain deviations e.g. a stem tilt towards varus, might increase bone stresses and PPF risk.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_5 | Pages 92 - 92
1 Apr 2018
Messer P Baetz J Lampe F Pueschel K Klein A Morlock M Campbell G
Full Access

INTRODUCTION

The restoration of the anatomical hip rotation center (HRC) has a major influence on the longevity of hip prostheses. Deviations from the HRC of the anatomical joint after total hip arthroplasty (THA) can lead to increased hip joint forces, early wear or loosening of the implant. The contact conditions of acetabular press-fit cups after implantation, including the degree of press-fit, the existence of a polar gap and cup orientation, may affect the HRC restoration, and therefore implant stability. The aim of this study was to determine the influence of acetabular press-fit, polar gap and cup orientation on HRC restoration during THA.

METHODS

THAs were performed by an experienced orthopaedic surgeon in full cadaveric models simulating real patient surgery (n=7). Acetabular cups with a Porocoat™ (n=3) and Gription™ surface coating (n=4) were implanted (DePuy Synthes, Leeds, UK). Computed tomography (CT) scans prior to surgery, as well as after reaming and implantation of press-fit cups were used to calculate the HRC displacement. After aligning the pelves in the anterior pelvic plane, 3D reconstruction of the HRC at each stage was performed by fitting spheres to the femoral head, the reamed cavity and the inserted cup. 3D surface models of the cups were generated using a laser scanner and were registered to the CT images. The effective press-fit was calculated using the diameters of spheres, fitted to the cavity prior to cup insertion and to the outer cup coating. The polar gap was defined as the difference between the outer cup surface and the subchondral bone at the cup pole. Anteversion and abduction angles were calculated as difference between the cup planes and the sagittal and transverse plane, respectively.


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_6 | Pages 4 - 4
1 Apr 2018
Baetz J Messer P Lampe F Pueschel K Klein A Morlock M Campbell G
Full Access

INTRODUCTION

Loosening is a major cause for revision in uncemented hip prostheses due to insufficient primary stability. Primary stability after surgery is achieved through press-fit in an undersized cavity. Cavity preparation is performed either by extraction (removing bone) or compaction (crushing bone) broaching. Densification of trabecular bone has been shown to enhance primary stability in human femora; however, the effect of clinically used compaction and extraction broaches on human bone with varying bone mineral density (BMD) has not yet been quantified. The purpose of this study was to determine the influence of the broach design and BMD on the level of densification at the bone-cavity interface, stem seating, the bone-implant contact area and the press-fit achieved.

METHODS

Paired human femora (m/f=11/12, age=60±18 y) were scanned with quantitative computed tomography (QCT, Philips Brilliance 16) before broaching, with the final broach, after its removal and after stem implantation. Compaction broaching (n=4) was compared in an in situ (cadaver) study against extraction broaching with blunt tooth types (n=3); in an ex situ (excised femora) study, compaction broaching was compared against extraction broaching with sharp tooth types (n=8 each). QCT data were resampled to voxel sizes of 1×1×1 mm (in situ) and 0.5×0.5×1 mm (ex situ). Mean trabecular BMD of the proximal femur was determined. The cavity volumes were segmented in the post-broach images (threshold: −250 mgHA/cm3, Avizo 9.2) and a volume of interest (VOI) of one-voxel thickness was added around the cavity to capture the interfacial bone. VOIs were transferred to the pre-broach image and bone densification was calculated within each VOI as the increase from pre- to post-broach image (MATLAB). Detailed surface data sets of broaches and stems were collected with a 3D laser-scanner (Creaform Handyscan 700) and aligned with the segmented components in the CT scans (Fig. 1). Stem seating was defined as the difference between the top edge of the stem coating and the final broach. Distance maps between the stem and cavity surface were generated to determine the bone-implant contact area and press-fit. All parameters were analysed between 5 mm distal to the coating and 1 cm distal to the lesser trochanter and analysed with related-samples Wilcoxon signed rank and Spearman's correlation tests (IBM SPSS Statistics 22).


Orthopaedic Proceedings
Vol. 99-B, Issue SUPP_20 | Pages 24 - 24
1 Dec 2017
Lampe F Marques C Lützner J
Full Access

Computer navigation in total knee arthroplasty (TKA) has proven to significantly reduce the number of outliers in prosthesis positioning and to improve mechanical leg alignment. Despite these advantages the acceptance of navigation technologies is still low among orthopaedic surgeons. The time required for navigation might be a reason for the low acceptance. The aim of the study was to test whether software and instrument improvements made in an established navigation system could lead to a significant navigation acquisition time reduction.

An improved and the current version of the TKA navigation software were used to perform surgery trials on a human cadaveric specimen by two experienced orthopaedic surgeons.

A significant effect of the “procedure” (navigation software version) on the navigation time (p< 0.001) was found, whereas the difference between surgeons was not significant (p= 0.2). There was no significant interaction between surgeon and navigation software version (p= 0.5). The improved version led to a significant navigation acquisition time reduction of 28%. Software and instrument improvements led to a statistically significant navigation acquisition time reduction. The achieved navigation acquisition time decrease was independent from surgeon.

Specific instrument and software improvements in established navigation systems may significantly decrease the surgery time segments where navigation takes place. However, the total navigation acquisition time is low in comparison to the total surgery time.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_I | Pages 124 - 124
1 Mar 2009
Lampe F Bohlen K Dries S Hille E
Full Access

Introduction: There is an ongoing discussion about potential risks and benefits of minimally invasive approaches (MIS) in total joint replacement. The aim of this study was to evaluate, whether a higher incidence of malalignments could be observed after minimally invasive navigated TKA and wether the results in the early postoperative period were better compared to standard approaches.

Methods: A total of 50 patients were treated with a navigated (OrthoPilot 4.2) Columbus knee prosthesis (BBraun Aesculap, Germany). In 25 patients either a standard or a minimally invasive (mini-mid-vastus) approach was carried out. In both groups the same exclusion criteria for MIS were adopted. Initially during surgery (Nav1a) and finally after implantation of the original components (Nav1b) the mechanical leg axis, passive range of motion and stability were measured by navigation according to the common workflow of the system. After restarting the software the same parameters were evaluated once more in a second procedure (Nav2) by reacquisition of joint centers both kinematically and by anatomical landmark palpation with the original prosthesis already implanted. Nav2 was conducted independantly from the initial surgical procedure. To validate the intraoperative measurements additional pre- and postoperative long-leg-standing radiographs were made. During the the first 10 days postoperatively daily range of motion (ROM) and pain (VAS) were measured. Perioperative blood loss and complications were documented. Results were analyzed by student’s t-test.

Results: Both groups were comparable with regard to preoperative demografic, radiologic and intraoperative data (Nav1a). There were no significant differences between the groups concerning intraoperative measurements of mechanical leg axis, passive range of motion and stability by Nav1b and Nav2. Additionally no differences were found for the alignment in the postoperative radiographs. The length of the skin incisions were significantly shorter in the minimally invasive group. Postoperative ROM was significantly higher and pain was significantly less intensive in the MIS group. Blood loss and complication rates were comparable.

Discussion: If the exclusion criteria for MIS were accepted no differences regarding the quality of alignment, passive range of motion and ligament stability could be demonstrated between conventional and MIS navigated TKA. Patients with MIS navigated TKA performed superior in terms of early p.o. function and pain. From the authors point of view the technically demanding minimally invasive implantation of knee prostheses should be exclusively performed with support of navigation.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 559 - 559
1 Aug 2008
Bohlen KE Lampe F Dries SPM Hille E
Full Access

Introduction: There is an ongoing discussion about potential risks and benefits of minimally invasive approaches (MIS) in total joint replacement. The aim of this study was to evaluate, whether a higher incidence of misalignments could be observed after minimally invasive navigated TKA and whether the results in the early postoperative period were better compared to standard approaches.

Methods: A total of 50 patients were treated with a navigated (OrthoPilot 4.2) Columbus knee prosthesis (BBraun Aesculap, Tuttlingen, Germany). In 25 patients either a standard or a minimally invasive (mini-mid-vastus) approach was carried out. In both groups the same exclusion criteria for MIS were adopted. Initially during surgery (Nav1a) and finally after implantation of the original components (Nav1b) the mechanical leg axis, passive range of motion and stability were measured by navigation according the common workflow of the system. After restarting the software the same parameters were evaluated once more in a second procedure (Nav2) by reacquisition of joint centres both kinematically and by anatomical landmark palpation with the original prosthesis already implanted. Nav2 was conducted independently from the initial surgical procedure. To validate the intraoperative measurements additional pre- and postoperative long-leg-standing radiographs were made. During the first 10 days postoperatively daily range of motion (ROM) and pain (VAS) were measured. Perioperative blood loss and complications were documented. Results were analyzed by student’s t-test.

Results: Both groups were comparable with regards to preoperative demographic, radiological and intraoperative data (Nav1a). There were no significant differences between the groups concerning intraoperative measurements of mechanical leg axis, passive range of motion and stability by Nav1b and Nav2. Additionally no differences were found for the alignment in the postoperative radiographs. The length of the skin incision was significantly shorter in the minimally invasive group. Postoperative ROM was significantly higher and pain was significantly less intensive in the MIS group. Blood loss and complication rates were comparable.

Discussion: If the exclusion criteria for MIS were accepted no differences regarding the quality of alignment, passive range of motion and ligament stability could be demonstrated between conventional and MIS navigated TKA. Patients with MIS navigated TKA performed superior in terms of early postoperative function and pain. From the authors point of view the technically demanding minimally invasive implantation of the knee prosthesis should be exclusively performed with support of navigation.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 559 - 559
1 Aug 2008
Lampe F Bohlen KE
Full Access

The video shows the detailed surgical technique of minimally invasive navigated total knee arthroplasty. A Columbus (BBraun Aesculap, Tuttlingen, Germany) total knee prosthesis is implanted using the OrthoPilot navigated system and the specially designed small MIOS instruments (BBraun Aesculap, Tuttlingen, Germany). A mini-mid-vastus approach is carried out with an 8 cm skin incision.