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Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_13 | Pages 35 - 35
1 Sep 2014
van der Merwe W van der Merwe J Hiddema W
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Background

Cup inclination is a major factor in the success of a total hip replacement. An open cup position can lead to dislocation or increased wear from rim loading and a closed cup position lead to impingement against the femoral neck or psoas. Although the ideal inclination for cup position is recommended as between 40 and 45 degrees, accurate positioning of the implant might be influenced by pelvic flexion and movement of the patient's pelvis during the procedure. We wanted to examine if the transvers acetabular ligament (TAL) could be used to determine cup inclination intra-operatively.

Methods

16 hips from 9 cadaveric specimens were used for the study. A computer navigation system (Brain lab) was used to measure and document the exact inclination and version of the acetabular trial component in three positions: flush with the transvers acetabular ligament (TAL), with the rim of the cup 5 mm from the TAL in a cranial direction and with the rim of the cup 5 mm caudally displaced. Statistical analysis of the results was performed by the Department of Biostatistics.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_14 | Pages 47 - 47
1 Mar 2013
Blake C Van Der Merwe J Human B
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Background

Using digital X-rays to plan a hip replacement can cause problems with sizing and templating the prosthesis. Using an AP view of both hips is desirable as this allows the use of the sometimes unaffected contralateral hip for templating.

Method

We devised a method of using a 20mm ball bearing as a marker positioned at the same depth as the greater trochanter, but between the patient's legs. Placing the marker between the patient's legs avoids the problem of the marker disappearing off the side of the X-ray, as is seen when placing the marker at the side of the obese patient. The marker is then used to calibrate the size of the digital X-ray. We used a hundred consecutive post-operative X-rays, comparing the size of the head of the femoral prosthesis used at surgery with the size measured pre-operatively using the marker.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_14 | Pages 85 - 85
1 Mar 2013
van der Merwe J Coetzer P
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Background

A variety of cerclage systems are available for the fixation of periprosthetic fractures. The aim of this study was to compare the forces applied by these systems.

Methods

We designed and manufactured a device to measure the forces applied to a cylindrical structure by a cerclage cable. Five different commonly used systems were evaluated. The forces exerted were measured at four different locations on the cylinder and this was compared to the force indicated by the tensioning device.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_III | Pages 493 - 493
1 Sep 2009
Pither C Foell J van der Merwe J Godwin P O’Dowd J White L
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Education is now recognised as a crucial component of the management of non specific low back pain. Mostly education is carried out informally in one to one consultations with health professionals. This has draw backs as it is costly, time limited, labour intensive and biased towards the discipline, training and beliefs of the clinician. The Back Book is a realistic alternative but provides very generic neutral information mostly promoting the message that pain isn’t damage.

We would see the process as one of the facilitation of knowledge acquisition rather than a formal teaching process. The latter implies engagement and responsibility on the part of the learner, rather than a pedagogic exercise by clinician or therapist.

We propose a group based, community delivered, interdisciplinary education module in which 4 different specialists contribute to an afternoon information session aimed at informing patients about: the causes of back pain from a non disease perspective, the complexity of pain perception, the biopsychosocial model, evidence based treatment of pain and some principles of paced pain management. The focus is on dispelling myths (such as the need for MRI scanning, surgery etc.) and enabling sufferers to make improved decisions about their care.

Data from over 120 patient attendances will be presented. These indicate high acceptability and satisfaction with 92% rating the afternoon as good or excellent and only 11% claiming the session had not helped them make better decisions about future treatment.

This model is simple, relatively low cost and accessible to primary care, which is acceptable and seemingly helpful to sufferers. It appears to be a viable model for presenting information to back pain sufferers early in their illness. The aim of this is to help them make more informed decisions and to see the need to incorporate self management approaches early in their history. More data are needed to ascertain whether these are achievable goals.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 471 - 472
1 Aug 2008
van Zyl A van der Merwe J
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1346 Primary TKR’s were evaluated. In keeping with the principle of Insall all patellas were resurfaced with the only exclusion being a previous patellectomy or excessive patella erosion.

Most TKR were of posterior cruciate substituting devices (IB11 (56.9%) or Nexgen LPS (42.3%)). The reason for operation was OA (94.5%), RA (2.9%), and others 2.6%. Most knees were in varus (68.5%), 17% were in valgus, and 14.5% were in neutral alignment.

The method of preparing the patella and extensor mechanism was as follows: A total fat pad excision was performed, debulking the patella thickness of 1mm. The patella component was placed medially and superiorly, a peri-patella synovectomy was performed, and a release of the lateral patella femoral ligaments was done. A lateral release was performed in 17.5% of patients.

Follow up ranges from 9 months to 15 years. Reoperation for patella problems was necessary in only 5 patients (0.37%). There was 1 case of patella subluxation, 1 case of persistent anterior knee pain, and 3 patients with a patella clunk (in IB 11 knees only)

In our hands this approach has led to excellent long term results without some of the potential complications described in the literature and warrants continued use of routine patella resurfacing when doing TKR.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 468 - 469
1 Aug 2008
van Zyl A van der Merwe J
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Knee sepsis following TKR can have devastating consequences for patient as well as surgeon. A two stage revision is a well accepted technique in TKR sepsis with the introduction of a temporary antibiotic cement spacer being the most popular procedure although irrigation techniques are popular in SA.

From a total of 111 revisions TKR from my practice 26 (23%) were 2 stage revisions for joint sepsis following TKR. 3 cases were early, 10 intermediate and 13 late onset sepsis cases. Most common organism was S. Aureus (7/26) and S. Epidermidis (7/26) although numerous other organisms were seen.

In all cases a two stage revision with a Palacos R cements spacer plus parenteral antibiotics were used. Prosthesis used for revision was primary knee prosthesis in 8 cases and revision (stemmed) prosthesis in 18 cases. Follow up range from 13 years to 6 months (average 6.8 years) with only one case of recurrent sepsis (3.8%) which went on to an arthrodesis. Time from debridement and spacer placement to revision TKR varied from 3 weeks to 10 months (average 2.1 months).

This paper shows that meticulous debridement followed by standard antibiotic cement spacer technique with additional parenteral antibiotics is indeed the gold standard approach without necessitating additional irrigation techniques.


Orthopaedic Proceedings
Vol. 87-B, Issue SUPP_III | Pages 278 - 278
1 Sep 2005
van Zyl A van der Merwe J Steyn R
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The number of worldwide THRs is growing but because we have no national register, the number done in South Africa is unknown. This is the third survey attempting to track the number of THRs done in this country. A survey 6 years ago indicated that 8986 THRs were done annually.

We sent out 521 questionnaires to members of the South African Orthopaedic Association. To date we have received 166 (31.86%) responses from members, 94 of whom perform THR. The data to date show that 4031 THRs are done annually, a mean of 42.88 operations per member.

Fully cemented THR is still the most popular form (58.3%), followed by hybrid (25.37%) and uncemented (15.85%). The most popular cements are Palacos (65%) and CMW (28%). Four prostheses lead the field at this stage: Elite Plus (27%), C-stem (9%), osteal (7%) and metal-on-metal resurfacing (6%).

We expect to have at least a 95% response by September 2004.


Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_IV | Pages 450 - 450
1 Apr 2004
van Zyl A van der Merwe J Snyman F
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Previous incisions around the knee may complicate subsequent total knee arthroplasty (TKA) because they can lead to skin problems, with wound breakdown and a risk of sepsis.

Our database contains details of 925 TKAs, 851 primary and 74 revision procedures. Of the 851 primary TKA patients, 368 had previously undergone knee surgery, 72 of them more than once. Twenty of the 74 patients who underwent revision TKA had undergone one previous procedure (excluding the primary TKA), and 24 had undergone multiple procedures. We clinically reviewed 133 TKAs, classifying previous procedures into midline (24), medial (50), lateral (26) and transverse (13) procedures. In 53 cases there had been previous arthroscopic procedures. Excluding the arthroscopies, previous scars were followed in 20 cases, partially followed in 11 cases and ignored in 53 cases.

Following up patients for a minimum of six months, we saw only six cases with minor wound edge slough. These did not require further surgery. Three of the six patients were in the group of 442 with previous scars, and three in the group of 483 without previous scars. All patients had spinal anaesthesia, peri-operative oxygen, vacuum drainage and a delayed knee-bending program, which we believe contributed to the low incidence of wound problems.

We believe that previous scars should be followed if they are approximately in the line of a normal midline TKA incision, and that scars beyond the midline can be ignored without increasing the risk of skin necrosis.


Orthopaedic Proceedings
Vol. 85-B, Issue SUPP_II | Pages 144 - 144
1 Feb 2003
van Zyl A van der Merwe J Snyman F
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Previous incisions around the knee may complicate subsequent total knee replacement (TKR) surgery because they can lead to skin problems, with wound breakdown and a risk of sepsis.

Our database contains details of 925 TKRs, 851 primary and 74 revision procedures. Of the 851 primary TKR patients, 368 had previously undergone knee surgery, 72 of them more than once. Twenty of the 74 patients who underwent revision TKR had undergone one previous procedure (excluding the primary TKR), and 24 had undergone multiple procedures. We clinically reviewed 133 TKRs, classifying previous procedures into midline (24), medial (50), lateral (26) and transverse (13) procedures. In 53 cases there had been previous arthroscopic procedures. Excluding the arthroscopies, previous scars were followed in 20 cases, partially followed in 11 cases and ignored in 53 cases.

Following up patients for a minimum of six months, we saw only six cases with minor wound edge slough. These did not require further surgery. Three of the six patients were in the group of 442 with previous scars, and three in the group of 483 without previous scars. All patients had spinal anaesthesia, peri-operative oxygen, vacuum drainage and a delayed knee-bending program, which we believe contributed to the low incidence of wound problems.

We believe that previous scars should be followed if they are approximately in the line of a normal midline TKR incision, and that scars beyond the midline can be ignored without increasing the risk of skin necrosis.