445 results found
Amis AA, Farahmand F, 1996, Biomechanics masterclass: extensor mechanism of the knee, Current Orthopaedics, Vol: 10, Pages: 102-109, ISSN: 0268-0890
WILLIAMS RJN, AMIS AA, 1995, A NEW-TYPE OF FLEXOR TENDON REPAIR - BIOMECHANICAL EVALUATION BY CYCLIC LOADING, ULTIMATE STRENGTH AND ASSESSMENT OF PULLEY FRICTION IN-VITRO, JOURNAL OF HAND SURGERY-BRITISH AND EUROPEAN VOLUME, Vol: 20B, Pages: 578-583, ISSN: 0266-7681
Williams RJ, Amis AA, 1995, A new type of flexor tendon repair. Biomechanical evaluation by cyclic loading, ultimate strength and assessment of pulley friction in vitro., J Hand Surg Br, Vol: 20, Pages: 578-583, ISSN: 0266-7681
Experiments were performed to evaluate biomechanical aspects of the performance of a "deep-biting peripheral suture" for flexor tendon repair, either when used alone or with a square or modified Kessler core stitch, and the technique was compared to the Kleinert repair. Tests included progressively increasing cyclic loads, force to pull the repair into the A2 pulley, and ultimate failure strength. 50% of the Kleinert repairs failed under 30 N cyclic loading, while 100% of the DBPS plus Kessler core stitch repairs survived. There was no discernable difference in gliding function or repair bulk between these sutures, but ultimate strength increased significantly with the DBPS repairs. We concluded that the DBPS plus Kessler-type core stitch will survive active mobilization better than the Kleinert method.
AMIS AA, MILLER JH, 1995, THE MECHANISMS OF ELBOW FRACTURES - AN INVESTIGATION USING IMPACT TESTS IN-VITRO, INJURY-INTERNATIONAL JOURNAL OF THE CARE OF THE INJURED, Vol: 26, Pages: 163-168, ISSN: 0020-1383
Amis AA, Zavras TD, 1995, Isometricity and graft placement during anterior cruciate ligament reconstruction, The Knee, Vol: 2, Pages: 5-17, ISSN: 0968-0160
This review paper starts with some basic definitions of anatomical positioning nomenclature and isometry, examines the reasons for aiming for isometry and discusses the tensile properties of ligaments and grafts in the light of length changes imposed by knee motion. An examination of the biomechanics of different tibial and femoral graft attachments, and the effects of errors from 'isometric' siting, leads into a review of previous literature of studies on the intact anterior cruciate ligament (ACL), ACL-deficient knees and then of ACL reconstructions. The discussion notes that there has been little work done to link the behaviour of reconstructed knees to that of the intact knees which the surgery is aiming to reproduce, and suggests that an anatomical graft placement, with the attachments eccentric to the isometric areas of intact knees, may approach this aim. © 1995.
Zavras TD, Mackenney RP, Amis AA, 1995, The natural history of anterior cruciate ligament reconstruction using patellar tendon autograft, The Knee, Vol: 2, Pages: 211-217, ISSN: 0968-0160
The purpose of this study was to review the results of ACL reconstruction using a patellar tendon graft placed 'over the top' plus a Macintosh lateral tenodesis, examining changes in knee laxity and functional status with increasing time. There were 74 patients operated on over an 11 year period, and divided into four groups for analysis according to postoperative time. There was a significant and progressive increase in side-to-side laxity difference with time, although functional status did not change significantly, indicating a lack of correlation between objective clinical tests and subjective findings. The highest Lysholm, Tegner and IKDC scores were at 4-5 years after operation, when 60% of patients were at their pre-injury level of sports activity. However, there was always a very significant difference between actual and desired Tegner activity levels for the group as a whole. While there was a significant correlation between degenerative changes and the time between injury and reconstruction, there was no correlation with postoperative time: this provides evidence that ACL reconstruction can protect the knee from later degeneration. © 1996.
RADFORD WJP, AMIS AA, HEATLEY FW, 1994, IMMEDIATE STRENGTH AFTER SUTURE OF A TORN ANTERIOR CRUCIATE LIGAMENT, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 76B, Pages: 480-484, ISSN: 0301-620X
Radford WJ, Amis AA, Heatley FW, 1994, Immediate strength after suture of a torn anterior cruciate ligament., J Bone Joint Surg Br, Vol: 76, Pages: 480-484, ISSN: 0301-620X
In an animal model we determined the strength of anterior cruciate ligaments (ACL) after section and repair by four different methods and compared it with that of the intact ligament. The standard suturing technique of multiple loops through the ligament stumps was used. Stronger suture material did not give a stronger repair. Wrapping a fine polyester mesh around the ligament or placing it between the bundles before suture increased the strength of the repair. This modification, allied to protective rehabilitation, may reduce the failure rate of acute ACL repairs.
RACE A, AMIS AA, 1994, THE MECHANICAL-PROPERTIES OF THE 2 BUNDLES OF THE HUMAN POSTERIOR CRUCIATE LIGAMENT, JOURNAL OF BIOMECHANICS, Vol: 27, Pages: 13-24, ISSN: 0021-9290
Harries W, Amis A, 1994, The Apex polyester fibre anterior cruciate ligament implant: operative procedure and early results, The Knee, Vol: 1, Pages: 209-215, ISSN: 0968-0160
This paper describes the surgical method and instruments for placing and anchoring the Apex polyester fibre anterior cruciate ligament (ACL) reconstruction. It then reviews the early clinical findings and describes recent developments. At the time of review, 172 Apex replacements had been implanted in the UK in arthroscopically proven chronic ACL-deficient knees. These had been inserted at eight centres since 1987, and follow up was by a single observer assessing patients by questionnaire, clinical examination, stress X-ray and KT 1000 arthrometer. Patients less than 12 months from surgery were excluded, leaving 95 with a mean follow up of 27 months (range 13 to 66 months) on whom results are based. Assessment showed improved stability after operation and the Apex implant appears to provide a reliable method of stabilizing the ACL deficient knee within the confines of this short-term review. The authors feel that further trials are justified. © 1995.
AMIS AA, 1994, THE MECHANICAL-PROPERTIES OF FINGER FLEXOR TENDONS AND DEVELOPMENT OF STRONGER TENDON SUTURING TECHNIQUES, NATO Advanced Research Workshop on Advances in the Biomechanics of the Hand and Wrist, Publisher: PLENUM PRESS DIV PLENUM PUBLISHING CORP, Pages: 41-57, ISSN: 0258-1213
Andersen HN, Amis AA, 1994, Review on tension in the natural and reconstructed anterior cruciate ligament., Knee Surg Sports Traumatol Arthrosc, Vol: 2, Pages: 192-202, ISSN: 0942-2056
This article reviews the methodology and results of published studies concerned with tension in the natural and reconstructed anterior cruciate ligament (ACL). This also includes studies of fiber length changes with knee motion and the relationships between graft tunnel placements and isometricity. Little work has been done in vivo: in humans, length changes of the anterior ACL fibers have been measured at operation, while animal longitudinal studies have been few and have given conflicting results. Work in vitro has used many methods to study ACL tension directly or indirectly, via length changes in fibers, but many authors have reported variable results, caused partly by inter-specimen differences and lack of control of forces or kinematics. It seems likely that different grafts require different peroperative tensions to restore normal stability when measured immediately after application at one knee position. But graft placement and the angle at which tensioning is performed also matter. Over-tensioning constrains knees under load cycling. Similarly, it is difficult to measure and therefore also to decide how tension should be distributed between an ACL graft and and augmentation to the graft. It was concluded that the published studies provide many guidelines for the effects of different graft placements or tensioning protocols but, overall, there is little firm evidence on which to recommend any particular ACL reconstruction protocol.
Amis AA, Beynnon B, Blankevoort L, et al., 1994, Proceedings of the ESSKA Scientific Workshop on Reconstruction of the Anterior and Posterior Cruciate Ligaments., Knee Surg Sports Traumatol Arthrosc, Vol: 2, Pages: 124-132, ISSN: 0942-2056
Amis AA, 1994, Development of the Apex polyester fibre cruciate ligament implant., Clin Mater, Vol: 15, Pages: 51-60, ISSN: 0267-6605
This paper describes the work done in developing the Apex polyester fibre cruciate ligament implant. A series of animal experiments showed that the material was the basis for good collagenous tissue ingrowth at the calcaneal tendon and within the knee joint. The rate of increase of strength of ingrowth at the calcaneal tendon was investigated. The slow maturation led to the development of a stainless steel screw and grommet anchorage system, which was also tested in vitro. A long-term animal study of the clinical implant and anchor system showed the implant fibres spaced apart by prolific ingrowth, while no implant particles were found, and there was no evidence of synovitis. The tissue reactions in human use have been found to be the same as in the animals, while ultrastructural study of retrieved specimens has given evidence of long-term collagen maturation.
Radford WJ, Amis AA, Kempson SA, et al., 1994, A comparative study of single- and double-bundle ACL reconstructions in sheep., Knee Surg Sports Traumatol Arthrosc, Vol: 2, Pages: 94-99, ISSN: 0942-2056
Work in vitro has previously shown superior restoration of knee stability using a double-bundle anterior cruciate ligament (ACL) reconstruction compared with single bundles taken through the condyle or 'over the top'. This paper describes an animal study designed to compare the three ACL reconstructions in vivo, in order to collect data that could support the clinical use of a double-bundle reconstruction. The three methods were compared in three groups of eight sheep, the ovine ACL having a distinct double-bundle structure. Biomechanically matched polyester fibre implants were used, with 6 months in vivo. The three methods led to similar intra-articular fibrous tissue integration of the implants and no evidence of implant damage, and biomechanical testing found greater laxity than normal for all three groups. The double-bundle group, however, had more joint surface degeneration than the other groups. It was concluded that clinical use of the double-bundle reconstruction was not indicated by the results of this experiment, in view of the more complex surgery and lack of superior performance.
AMIS AA, SCAMMELL BE, 1993, BIOMECHANICS OF INTRAARTICULAR AND EXTRAARTICULAR RECONSTRUCTION OF THE ANTERIOR CRUCIATE LIGAMENT, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 75, Pages: 812-817, ISSN: 0301-620X
KNIGHT DJ, RYMASZEWSKI LA, AMIS AA, et al., 1993, PRIMARY REPLACEMENT OF THE FRACTURED RADIAL HEAD WITH A METAL PROSTHESIS, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 75, Pages: 572-576, ISSN: 0301-620X
AMIS AA, CAMBURN M, KEMPSON SA, et al., 1993, ANTERIOR CRUCIATE LIGAMENT REPLACEMENT WITH POLYESTER FIBER - A LONG-TERM STUDY OF TISSUE-REACTIONS AND JOINT STABILITY IN SHEEP (J BONE SURG, VOL 74-B, PG 605, 1992), JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 75, Pages: 169-169, ISSN: 0301-620X
Amis AA, Camburn M, Kempson SA, et al., 1993, Correction: Anterior cruciate ligament replacement with polyester fibre: A long-term study of tissue reactions and joint stability in sheep (Journal of Bone and Joint Surgery [Br] (1992) 74-B (605-613)), Journal of Bone and Joint Surgery - Series B, Vol: 75, ISSN: 0301-620X
AMIS AA, CAMBURN M, KEMPSON SA, et al., 1992, ANTERIOR CRUCIATE LIGAMENT REPLACEMENT WITH POLYESTER FIBER - A LONG-TERM STUDY OF TISSUE-REACTIONS AND JOINT STABILITY IN SHEEP, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 74, Pages: 605-613, ISSN: 0301-620X
Sward L, Hughes JS, Amis A, et al., 1992, The strength of surgical repairs of the rotator cuff. A biomechanical study on cadavers., J Bone Joint Surg Br, Vol: 74, Pages: 585-588, ISSN: 0301-620X
Using 26 cadaver shoulders, we produced a standard defect in the supraspinatus tendon and performed one of three types of repair. Their strength was found by testing in tension the force required to produce a gap of 3 mm, then 6 mm, and finally total disruption of the repair. The use of a polyethylene patch to spread the forces over the lateral bone surface and of extra sutures to grasp the tendon end raised by 2.6 times the load at which a 3 mm gap in the repair occurred and by 1.7 times the load to failure.
MASHADI ZB, AMIS AA, 1992, VARIATION OF HOLDING STRENGTH OF SYNTHETIC ABSORBABLE FLEXOR TENDON SUTURES WITH TIME, JOURNAL OF HAND SURGERY-BRITISH AND EUROPEAN VOLUME, Vol: 17B, Pages: 278-281, ISSN: 0266-7681
Mashadi ZB, Amis AA, 1992, Variation of holding strength of synthetic absorbable flexor tendon sutures with time., J Hand Surg Br, Vol: 17, Pages: 278-281, ISSN: 0266-7681
This study examined the potential use of absorbable polytrimethylene carbonate (Maxon) sutures for tendon surgery. Flexor tendons of the third toe of 48 chickens were transected and sutured, then evaluated both mechanically and histologically at 0, five, 15 and 45 days after operation. Mechanical testing showed that the suture kept its strength long enough to unite tendon ends. However, high tissue reactivity of polytrimethylene carbonate during its dissolution caused adhesions.
MASHADI ZB, AMIS AA, 1992, STRENGTH OF THE SUTURE IN THE EPITENON AND WITHIN THE TENDON FIBERS - DEVELOPMENT OF STRONGER PERIPHERAL SUTURE TECHNIQUE, JOURNAL OF HAND SURGERY-BRITISH AND EUROPEAN VOLUME, Vol: 17B, Pages: 172-175, ISSN: 0266-7681
Mashadi ZB, Amis AA, 1992, Strength of the suture in the epitenon and within the tendon fibres: development of stronger peripheral suture technique., J Hand Surg Br, Vol: 17, Pages: 172-175, ISSN: 0266-7681
In tendon repair, the peripheral stitches are usually placed in the epitenon, but it has not yet been defined whether the grasping strength of the sutures in the epitenon and within the tendon fibres are different. The first stage of this work investigated this difference and found that peripheral stitches within cadaveric tendon fibres were 83% stronger than those in the epitenon layer. A new peripheral stitch, based on this finding, has been designed. Mechanical tests of a range of peripheral suture types in vitro found that the new technique gave a resistance to gap formation twice that of the peripheral stitches commonly in use at present and a rupture strength more than three times, while still avoiding eversion problems.
Wetherell RG, Unsworth A, Amis AA, 1992, The function of bipolar hip prostheses--a laboratory study using cadaveric acetabula., Proc Inst Mech Eng H, Vol: 206, Pages: 37-42, ISSN: 0954-4119
Cadaveric acetabula were mounted in a hip simulator and the friction developed in each during articulation with a series of metal femoral head prostheses of differing sizes was measured. In a separate study, assembled Hastings bipolar hip prostheses were subjected to weight-bearing forces in the same acetabula and their self-righting mechanism was observed. The self-righting mechanism was found to function efficiently, in most cases overcoming the combined friction of the inner and outer articulations of the Hastings hip. However, during motion in the hip simulator a wide variation of friction was observed between different acetabula and within the same acetabulum with differing head size. In several cases this acetabular friction was found to be less than the friction in the inner articulation of the Hastings bipolar hip prosthesis, and this may explain some cases of reported failure of biarticular function.
STEAD AC, AMIS AA, CAMPBELL JR, 1991, USE OF POLYESTER FIBER AS A PROSTHETIC CRANIAL CRUCIATE LIGAMENT IN SMALL ANIMALS, JOURNAL OF SMALL ANIMAL PRACTICE, Vol: 32, Pages: 448-454, ISSN: 0022-4510
AMIS AA, DAWKINS GPC, 1991, FUNCTIONAL-ANATOMY OF THE ANTERIOR CRUCIATE LIGAMENT - FIBER BUNDLE ACTIONS RELATED TO LIGAMENT REPLACEMENTS AND INJURIES, JOURNAL OF BONE AND JOINT SURGERY-BRITISH VOLUME, Vol: 73, Pages: 260-267, ISSN: 0301-620X
MASHADI ZB, AMIS AA, 1991, THE EFFECT OF LOCKING LOOPS ON THE STRENGTH OF TENDON REPAIR, JOURNAL OF HAND SURGERY-BRITISH AND EUROPEAN VOLUME, Vol: 16B, Pages: 35-39, ISSN: 0266-7681
Mashadi ZB, Amis AA, 1991, The effect of locking loops on the strength of tendon repair., J Hand Surg Br, Vol: 16, Pages: 35-39, ISSN: 0266-7681
A multiple X-raying method has been developed which allows examination of how the particular features of suturing techniques collapse or pull out of the tendon during tensile testing. This technique was used to examine the locking loop tendon sutures, such as the modified Kessler, Verdan and Ketchum techniques. Locking loops did not contribute towards the strength when small diameter sutures (5/0) of various materials were applied to the tendon, collapsing at 12 Newtons. Larger diameter sutures (4/0) slightly reduced the risk of failure of locking loops, but they still collapsed at 15 Newtons or less, so suture techniques which depend on locking loops will often lead to gap formation at low loads and hence poor results.
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