We hypothesised that the removal of the subchondral bone plate (SCBP) for cemented acetabular component fixation in total hip arthroplasty (THA) offers advantages over retention by improving the cement-bone interface, without jeopardising implant stability. We have previously published two-year follow-up data of a randomised controlled trial (RCT), in which 50 patients with primary osteoarthritis were randomised to either retention or removal of the SCBP. The mean age of the retention group (n = 25, 13 males) was 70.0 years (sd 6.8). The mean age in the removal group (n = 25, 16 males) was 70.3 years (sd 7.9). Now we have followed up the patients at six (retention group, n = 21; removal group, n = 20) and ten years (retention group: n = 17, removal group: n = 18), administering clinical outcome questionnaires and radiostereometric analysis (RSA), and determining the presence of radiolucent lines (RLLs) on conventional radiographs. RSA demonstrated similar translation and rotation patterns up to six years. Between six and ten years, proximal acetabular component migration and changes of inclination were larger in the retention group, although the mean differences did not reach statistical significance. Differences in migration were driven by two patients in the SCBP retention group with extensive migration versus none in the SCBP removal group. The significant difference (p < 0.001) in the development of radiolucent lines in the retention group, previously observed at two years, increased even further during the course of follow-up (p < 0.001). While recognising SCBP removal is a more demanding technique, we conclude that, wherever possible, the SCBP should be removed to improve the cement–bone interface in order to maximise acetabular component stability and longevity.

Cite this article: Bone Joint J 2015;97-B:35–44.

Progressive retroversion of a cemented stem is predictive of early loosening and failure. We assessed the relationship between direct post-operative stem anteversion, measured with CT, and the resulting rotational stability, measured with repeated radiostereometric analysis over ten years. The study comprised 60 cemented total hip replacements using one of two types of matt collared stem with a rounded cross-section. The patients were divided into three groups depending on their measured post-operative anteversion (< 10°, 10° to 25°, >  25°). There was a strong correlation between direct post-operative anteversion and later posterior rotation. At one year the < 10° group showed significantly more progressive retroversion together with distal migration, and this persisted to the ten-year follow-up. In the < 10° group four of ten stems (40%) had been revised at ten years, and an additional two stems (20%) were radiologically loose. In the ‘normal’ (10° to 25°) anteversion group there was one revised (3%) and one loose stem (3%) of a total of 30 stems, and in the > 25° group one stem (5%) was revised and another loose (5%) out of 20 stems. This poor outcome is partly dependent on the design of this prosthesis, but the results strongly suggest that the initial rotational position of cemented stems during surgery affects the subsequent progressive retroversion, subsidence and eventual loosening. The degree of retroversion may be sensitive to prosthetic design and stem size, but < 10° of anteversion appears deleterious to the long-term outcome for cemented hip prosthetic stems.

Cite this article: Bone Joint J 2013;95-B:23–30.

We present a new approach for the accurate reconstruction of three-dimensional skeletal positions using roentgen single-plane photogrammetric analysis (RSPA). This technique uses a minimum of three markers embedded in each segment which allow continuous, real-time, internal skeletal movement to be measured from single-plane images, provided that the precise distance between the markers is known.

A simulation study indicated that the error propagation in this approach is influenced by focus position, object position, the number of control points, the accuracy of the previous measurement of the distance between markers and the accuracy of image measurement. For reconstruction of normal movement of the knee with an input measurement error of sd = 0.02 mm, the rotational and translational differences between reconstructed and original movement were less than 0.27° and 0.9 mm, respectively.

Our results showed that the accuracy of RSPA is sufficient for the analysis of most movement of joints. This approach can be applied in combination with force measurements for dynamic studies of the musculoskeletal system.

The Swedish Knee Arthroplasty Registry (SKAR) has recorded knee arthroplasties prospectively in Sweden since 1975. The only outcome measure available to date has been revision status. While questionnaires on health outcome may function as more comprehensive endpoints, it is unclear which are the most appropriate. We tested various outcome questionnaires in order to determine which is the best for patients who have had knee arthroplasty as applied in a cross-sectional, discriminative, postal survey.

Four general health questionnaires (NHP, SF-12, SF-36 and SIP) and three disease/site-specific questionnaires (Lequesne, Oxford-12, and WOMAC) were tested on 3600 patients randomly selected from the SKAR. Differences were found between questionnaires in response rate, time required for completion, the need for assistance, the efficiency of completion, the validity of the content and the reliability. The mean overall ranks for each questionnaire were generated. The SF-12 ranked the best for the general health, and the Oxford-12 for the disease/site-specific questionnaires. These two questionnaires could therefore be recommended as the most appropriate for use with a large knee arthroplasty database in a cross-sectional population.

To assess migration of the tibial component we used roentgen stereophotogrammetric analysis in 40 patients who had had a total knee arthroplasty after failure of a closing wedge osteotomy and compared them with 40 matched patients after primary total knee arthroplasty.

We found no difference in migration over time or in the tendency for continuous migration between the two groups. There were no differences in alignment or position of the knee prosthesis or in the clinical outcome.

Our findings show that revision of a failed high tibial osteotomy to a total knee arthroplasty is effective.

We obtained simultaneous measurements of sagittal knee laxity in 12 consecutive patients after reconstruction of the anterior cruciate ligament (ACL), using the Stryker laxity tester and radiostereometric analysis (RSA).

The mean anteroposterior (AP) displacement when a 90 N load was applied in both directions was 5.3 ± 2.7 mm with RSA and 9.8 ± 1.6 mm with the external device (p < 0.001). The corresponding measurements at a load of 180 N were 5.7 ± 2.4 mm and 13.8 ± 3.7 mm, respectively (p < 0.001).

More than 50% of the sagittal knee movement, as measured by the external device at a load of 180 N, was not true femorotibial displacement of the joint but was due to soft-tissue deformation.

We report a prospective study of gait and tibial component migration in 45 patients with osteoarthritis treated by total knee arthroplasty (TKA). Migration was measured over two years using roentgen stereophotogrammetry. We used the previously established threshold of 200 μm migration in the second postoperative year to distinguish two groups: a risk group of 15 patients and a stable group of 28 patients.

We performed gait analysis before operation and at six months and at two years after TKA. On all three occasions we found significant differences between the two groups in the mean sagittal plane moments of the knee joint. The risk group walked with higher peak flexion moments than the stable group. The two groups were not discriminated by any clinical or radiological criteria or other gait characteristics.

The relationship which we have found between gait with increased flexion moments and risk of tibial component loosening warrants further study as regards the aetiology of prosthetic loosening and possible methods of influencing its incidence.

The tibial components in 143 patients with total knee replacements performed before 1988 were assessed for micromotion using roentgen stereophotogrammetric analysis (RSA) over a period of 13 years. The fixation of the prostheses remained clinically sound in all cases, although revision had been required for other reasons in seven. In a second group taken from all cases with RSA available on our full database to 1990, 15 tibial components had been followed by RSA from the insertion until, 1 to 11 years after the initial arthroplasty, they were revised for mechanical loosening of the tibial component; 12 of these comprised all the loosenings in the base group, thus making a total of 155 consecutive cases, while an additional three were inserted after the base material had been compiled. The mean migration in the first group was about 1 mm at one year, but subsequent migration was slower, reaching a mean of about 1.5 mm after ten years. About one-third migrated continuously throughout follow-up, while two-thirds ceased to migrate after one to two years. In the revision group, 14 components had migrated continuously and at one year significantly more than those in the first group. One revision case lacked the crucial one-year follow-up and could not be classified. These findings suggest that mechanical loosening begins early in the postoperative period. Clinical symptoms which necessitate revision, seen at this stage in 20% of abnormally migrating tibial components, may not appear until up to ten years after the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

We allocated randomly 27 patients undergoing 28 primary uncemented total hip replacements (THR) to receive prosthetic components of similar design with either plasma-sprayed titanium alloy (Ti) coating (n = 13) or hydroxyapatite (HA) coating (n = 15). After some exclusions, 15 of the patients (15 THR; 7 with HA- and 8 with Ti-coating) were followed by roentgen stereophotogrammetric analysis at 3, 6 and 12 months to measure migration of the femoral component. Twenty-six of the patients (26 THR) were followed clinically and by conventional radiography. All the femoral components had migrated at 3 months. From 3 to 12 months, the migration of Ti-coated components continued whereas the HA-coated components had stabilised. At 12 months there was significantly less migration of the HA-coated components (p < 0.05). The maximum subsidence was 0.2 mm in both groups. The Harris hip score was equal in the two groups preoperatively but at follow-up it was better in the HA-coated group (p < 0.05) and visual analogue scale scores showed that they had less pain (p < 0.05).

We studied the effect of a layer of cement placed under the tibial component of Freeman-Samuelson total knee prostheses with a metal back and an 80 mm intramedullary stem, using roentgen stereophotogrammetry to measure the migration of the tibial component during one year in 13 uncemented and 16 cemented knees. The addition of cement produced a significant reduction in migration at one year, from a mean of 1.5 mm to one of 0.5 mm (p less than 0.01), including a significant reduction in pure subsidence. One year postoperatively the clinical results were similar between the groups, but, at three years, one uncemented knee had required revision.

From 1970 to 1978, 29 patients had a unilateral operation for bilateral recurrent dislocation of the patella. We examined 21 of them at a mean of 14 years postoperatively. Eighteen of these patients had evidence of generalised joint laxity. Six of the operated knees and four of the unoperated knees still had recurrent dislocations. The operated knees were clinically worse, with a significantly higher incidence of osteoarthritis. We concluded that the operations used to treat recurrent dislocation of the patella may have had short-term benefits, but did not cure the patients in the long term.

A saw blade was made from two standard oscillating blades which were fixed to each other with channels between, so that cooling fluid could be directed to the saw teeth. The blade was connected to a standard arthroscopy pump which delivered a flow of 80 ml/min through the blade. The performance of this blade was compared with that of a standard saw blade, cutting ox-bone in the laboratory. Irrigation of the standard saw blade with saline delivered by a syringe only slightly diminished the maximum temperature. Pumped irrigation was more effective but required large volumes of fluid. The heat generated by the internally cooled saw blade was negligible and the temperatures achieved (19 degrees C to 34 degrees C) fell well below the critical level for bone death (44 degrees C to 47 degrees C).

We studied the effect of a metal tray with an intramedullary stem on the micromotion of the tibial component in total knee arthroplasty. Of 32 uncemented Freeman-Samuelson knee arthroplasties performed in London and Gothenburg, nine had a metal backing and stem added to the tibial component. Micromotion of the tibial components, expressed as migration and inducible displacement, was analysed using roentgen stereophotogrammetric analysis up to two years follow-up. The addition of a metal back and a 110 mm stem to the standard polyethylene component significantly reduced both migration over two years and inducible displacement.