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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 160 - 160
1 Sep 2012
Blakeney W Khan R Lam L Breidahl W
Full Access

Background

The long-term impact of dividing Piriformis when performing a standard posterior approach to the hip has not been assessed. A less invasive approach in which the tendon is preserved has been described (the Piriformis-sparing minimally invasive [PSMI] approach). With advances in MRI technology it is now possible to image structures in close proximity to metal without artifact. The aim of the study was to compare the MRI features (muscle grade and bulk) of the divided and repaired Piriformis tendon group (by the standard posterior approach) with the preserved tendon group (by the PSMI approach).

Methods

As part of an on-going randomized controlled trial comparing the PSMI approach with the standard posterior approach for total hip replacement, a subgroup of 20 consecutive patients who fulfilled the inclusion criteria were recruited. Patients received preoperative and 3 months and 2 year postoperative MRI scans. Patients and evaluators were blinded to allocation. Outcomes assessed included grade, volume and integrity of Piriformis.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_I | Pages 7 - 7
1 Mar 2008
Chauhan S Scott R Breidahl W Beaver R
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To compare the new technique of computer assisted knee arthroplasty (CAK) against the current gold standard conventional jig based technique (JBK), 75 consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. The CAK surgery was performed using a freehand technique that avoids violation of the medullary canal. Pre-and post-operative Knee society scores were collected. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol and pre-and post-operative Maquet views of the limb performed. Intra-operative soft tissue release together with postoperative pain scores and blood loss were also assessed.

CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032), femoral rotation (p=0.001), tibial varus/ valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoral-tibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer, a mean increase of 13 minutes (p=0.0001).

This is the first controlled study to assess all seven-alignment characteristics of knee arthroplasty in these two groups of patients.

The improvement in alignment resulted in this trial being stopped prematurely as 6 out of 7 of the initial variables had reached significance. It shows a clear improvement in component alignment with computer navigation. The reduction in blood loss in this surgery through not violating the medullary canal will also be beneficial.


The Journal of Bone & Joint Surgery British Volume
Vol. 89-B, Issue 9 | Pages 1165 - 1171
1 Sep 2007
Gohil S Annear PO Breidahl W

Animal studies have shown that implanted anterior cruciate ligament (ACL) grafts initially undergo a process of revascularisation prior to remodelling, ultimately increasing mechanical strength. We investigated whether minimal debridement of the intercondylar notch and the residual stump of the ruptured ACL leads to earlier revascularisation in ACL reconstruction in humans. We undertook a randomised controlled clinical trial in which 49 patients underwent ACL reconstruction using autologous four-strand hamstring tendon grafts. Randomised by the use of sealed envelopes, 25 patients had a conventional clearance of the intercondylar notch and 24 had a minimal debridement method. Three patients were excluded from the study. All patients underwent MR scanning postoperatively at 2, 6 and 12 months, together with clinical assessment using a KT-1000 arthrometer and International Knee Documentation Committee (IKDC) evaluation. All observations were made by investigators blinded to the surgical technique. Signal intensity was measured in 4 mm diameter regions of interest along the ACL graft and the mid-substance of the posterior cruciate ligament.

Our results indicate that minimal debridement leads to earlier revascularisation within the mid-substance of the ACL graft at two months (paired t-test, p = 0.002). There was a significant reduction of mid-substance signal six months after the minimal debridement technique (paired t-test, p = 0.00007). No statistically significant differences were found in tunnel placement, incidence of Cyclops lesions, blood loss, IKDC scores, range of movement or Lachman test between the two groups.


The Journal of Bone & Joint Surgery British Volume
Vol. 86-B, Issue 6 | Pages 818 - 823
1 Aug 2004
Chauhan SK Clark GW Lloyd S Scott RG Breidahl W Sikorski JM

A controlled study, comparing computer- and conventional jig-assisted total knee replacement in six cadavers is presented. In order to provide a quantitative assessment of the alignment of the replacements, a CT-based technique which measures seven parameters of alignment has been devised and used. In this a multi-slice CT machine scanned in 2.5 mm slices from the acetabular roof to the dome of the talus with the subject’s legs held in a standard position. The mechanical and anatomical axes were identified, from three-dimensional landmarks, in both anteroposterior and lateral planes. The coronal and sagittal alignment of the prosthesis was then measured against the axes. The rotation of the femoral component was measured relative to the transepicondylar axis. The rotation of the tibial component was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The radiation dose was 2.7 mSV.

The computer-assisted total knee replacements showed better alignment in rotation and flexion of the femoral component, the posterior slope of the tibial component and in the matching of the femoral and tibial components in rotation. Differences were statistically significant and of a magnitude that support extension of computer assistance to the clinical situation.


The Journal of Bone & Joint Surgery British Volume
Vol. 86-B, Issue 3 | Pages 372 - 377
1 Apr 2004
Chauhan SK Scott RG Breidahl W Beaver RJ

We have compared a new technique of computer-assisted knee arthroplasty with the current conventional jig-based technique in 70 patients randomly allocated to receive either of the methods. Post-operative CT was performed according to the Perth CT Knee Arthroplasty protocol and pre- and post-operative Maquet views of the limb were taken. Intra-operative and peri-operative morbidity data were collected and blood loss measured.

Post-operative CT showed a significant improvement in the alignment of the components using computer-assisted surgery in regard to femoral varus/valgus (p = 0.032), femoral rotation (p = 0.001), tibial varus/valgus (p = 0.047) tibial posterior slope (p = 0.0001), tibial rotation (p = 0.011) and femorotibial mismatch (p = 0.037). Standing alignment was also improved (p = 0.004) and blood loss was less (p = 0.0001). Computer-assisted surgery took longer with a mean increase of 13 minutes (p = 0.0001).


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_IV | Pages 442 - 442
1 Apr 2004
Chauhan S Clark G Scott R Lloyd S Sikorski J Breidahl W
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Introduction: We describe a CT method that allows the seven alignment characteristics of a knee arthroplasty to be defined in a single investigation.

Method: A multislice CT scanner, scans in 2.5mm slices from the acetabular roof to the dome of the talus with the legs in a standard position.

The mechanical and anatomical axes are identified, from 3 dimensional landmarks, in both AP and lateral planes. The coronal and sagittal alignment of the pros-theses is then measured against the axes.

The rotation of the femoral component is measured relative to the transepicondylar axis. Tibial rotation was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images.

The results of 100 scans show a low inter and intra observer error rate whilst independent assessment shows a mean measurement error of 3mm in a three dimensional plane. The radiation dose is 2.7mSV.

Conclusions: The technique provides the only currently available measure of all the alignment characteristics required to assess the quality of a knee arthroplasty. It will become a gold standard in planning revision surgery and provide a valuable tool in assessing alignment of painful knee replacements.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_IV | Pages 475 - 475
1 Apr 2004
Beaver R Chauhan S Scott R Breidahl W Sikorski J
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Introduction The aim of this study was to compare the new technique of computer assisted knee arthroplasty (CAK) against the conventional jig based technique (JBK).

Methods Seventy-five consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol to assess the accuracy of alignment. This measures seven parameters of alignment to an accuracy of one degree. Pre and post-operative Maquet views of the limb were also performed. Intra-operative soft tissue release together with post-operative pain scores and blood loss where also assessed.

Results CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032),femoral rotation (p=0.001),tibial varus/valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoraltibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer, a mean increase of 13 minutes (p=0.0001).

Conclusions This is the first controlled study to assess all seven alignment characteristics of knee arthroplasty and use them to compare outcomes in conventional and computer assisted operations. It shows a clear improvement in component alignment with computer navigation.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_III | Pages 359 - 359
1 Mar 2004
Chauhan S Clark G Scott R Sikorski J Breidahl W
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Introduction: Plain radiographs are a poor indication of the overall axial and rotational alignment of a total knee replacement. A CT method is described to overcome these problems. Method: A multislice CT scanner took 1mm contingous slices from the acetabular roof to the dome of the talus with the legs immobile in a standard position. The scans are stored and reformatted to allow axial, coronal and sagittal images. The centre of femoral head, distal femur, tibial plateau and ankle joints are identiþed in three dimensions. The mechanical and anatomical axes are identiþed. The alignment of the prostheses is then measured against the mechanical axis in both AP and lateral planes. The rotation of the femoral component is measured relative to the transepicondylar axis. Tibial rotation was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The accuracy of this technique has been checked by using a Ferro Arm which mechanically validates the mechanical axis. Results: The technique provides the only currently available measure of all the alignment characteristics required to assess the quality of a knee replacement. Conclusions: The Perth protocol provides an accurate assessment of alignment of the femoral and tibial components to a measured mechanical axis and rotational measurements of both components both individually and