David G. Campbell

Total knee replacement in the morbidly obese: a literature review.

Background:u2002 The ‘obesity epidemic’ is expected to result in an increased incidence of knee osteoarthritis and hence total knee replacements (TKRs). Reviews have demonstrated the conflicting results of TKR for all obese (body mass index (BMI) >30). The aim of this literature review was to specifically evaluate outcomes of TKR in patients with morbid obesity (MO; BMI >40).

Patient-perceived outcome measures following unicompartmental knee arthroplasty with mini-incision.

We reviewed 150 patients (183 knees) who underwent mini-incision unicompartmental knee arthroplasty (Oxford). Mean age was 71.5 (36–92) years. Review was conducted at least 12 months following surgery. To assess results, we used the Oxford knee questionnaire, modified Grimby score, return to sport and work, knee “normality” and patient general health. The mean Oxford knee score was 22.17 (range 12–54). Kneeling scored worse than other activities. No significant age or gender difference was found. Mean modified Grimby score was 3.89, equating to moderate exercise less than 2xa0h a week. Patients with “artificial-feeling” knees had significantly worse scores than patients with normal/near-normal-feeling knees. Patients who returned to/increased sporting activity had better Oxford scores than those who did not. Ninety-four percent of patients working pre-operatively returned to work. Sixty-seven percent continued at the same level of or increased sporting activity. Oxford knee scores and return to sport compared well to published data. Results regarding modified Grimby score, return to work and pain relief were encouraging. The best results were achieved in active patients who felt their health was good and their knee felt normal or near normal following surgery.RésuméNous avons examiné 150 malades (183 genoux) qui ont subi une arthroplastie unicompartmentale (Oxford) par une mini-incision. L’âge moyen était 71,5 ans (36–92). L’examen a été conduit au moins 12 mois après la chirurgie. Nous avons utilisé le questionnaire de genou Oxford, le score modifié de Grimby, le retour au sport et au travail, la “normalité” du genou et la santé générale du malade. Le score moyen d’Oxford était 22.17 (12–54). Le défaut d’agenouilllement était le plus péjoratif. Aucune différence notable de sexe ou d’age n’a été trouvée. Le score moyen modifié de Grimby était 3.89, équivalent à un exercice modéré moins de deux heures par semaine. Les malades avec la sensation de genou “artificiel” avaient des scores nettement moins bons que les malades ayant la sensation d’un genou normal ou proche de la normale. Les malades qui avaient retrouvé ou augmenté l’activité sportive avaient un meilleur score d’Oxford que les autres. Ninety-fourpercentage des malades travaillant avant l’opération ont repris le travail après. 67% des malades ont continué au même niveau de sport ou ont augmenté l’activité sportive. Les scores d’Oxford et le retour au sport étaient comparables aux données publiées. Les résultats selon le score modifié de Grimby, le retour au travail et la disparition des douleurs étaient encourageant. Les meilleurs résultats ont été obtenus chez des patients actifs, en bonne santé, et qui ont senti leur genou comme normal ou sub-normal après l’opération.

Early migration characteristics of a hydroxyapatite-coated femoral stem: an RSA study

Measurement of early stem subsidence can be used to predict the likelihood of long-term femoral component loosening and clinical failure. Data that examines the early migration pattern of clinically proven stems will provide clinicians with useful baseline data with which to compare new stem designs. This study was performed to evaluate the early migration pattern of a hydroxyapatite-coated press-fit femoral component that has been in use for over tenxa0years. We enrolled 30 patients who underwent THA for osteoarthritis. The median age was 70xa0years (range, 55–80xa0years). Patients were clinically assessed using the Harris hip score. Radiostereometric analysis was used to evaluate stem migration at three to fourxa0days, sixxa0months, onexa0year and twoxa0years. We observed a mean subsidence of 0.73xa0mm at sixxa0months, 0.62xa0mm at onexa0year and 0.58xa0mm at twoxa0years and a mean retroversion of 1.82° at sixxa0months, 1.90° at onexa0year and 1.59° at twoxa0years. This data suggests that subsidence is confined to the first sixxa0months after which there was no further subsidence. The results from this study can be compared with those from novel cementless stem designs to help predict the long-term outcome one may expect from new cementless stem designs.

Second-generation Highly Cross-linked X3™ Polyethylene Wear: A Preliminary Radiostereometric Analysis Study

BackgroundFirst-generation highly cross-linked polyethylene liners have reduced the incidence of wear particle-induced osteolysis. However, failed acetabular liners have shown evidence of surface cracking, mechanical failure, and oxidative damage. This has led to the development of second-generation highly cross-linked polyethylene, which has improved wear and mechanical properties and resistance to oxidation in vitro. Owing to its recent introduction, there are no publications describing its clinical performance.Questions/purposesWe assessed early clinical wear of a second-generation highly cross-linked polyethylene liner and compared its clinical performance with the published results of hip simulator tests and with first-generation highly cross-linked polyethylene annealed liners.Patients and MethodsTwenty-one patients were enrolled in a prospective cohort study. Clinical outcome and femoral head penetration were measured for 19 patients at 6xa0months and 1 and 2xa0years postoperatively.ResultsThe median proximal head penetration was 0.009xa0mm and 0.024xa0mm at 1 and 2xa0years, respectively. The median two-dimensional (2-D) head penetration was 0.083xa0mm and 0.060xa0mm at 1 and 2xa0years, respectively. The median proximal wear rate between 1 and 2xa0years was 0.015xa0mm/year.ConclusionsThe wear rate calculated was similar to the in vitro wear rate reported for this material; however, it was less than the detection threshold for this technique. Although longer followup is required for wear to reach a clinically quantifiable level, this low level of wear is encouraging for the future clinical performance of this material.Level of EvidenceLevel IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Low Wear of a Second-generation Highly Crosslinked Polyethylene Liner: A 5-year Radiostereometric Analysis Study

BackgroundA sequentially irradiated and annealed, second-generation highly crosslinked polyethylene (XLPE) liner was introduced clinically in 2005 to reduce in vivo oxidation. This liner design has also been shown to reduce wear in vitro when compared with conventional and first-generation crosslinked liners. To date, there is only one study reporting an in vivo wear rate of this liner at 5xa0years’ followup. However, that study used measurements made from plain radiographs, which have limited sensitivity, particularly when monitoring very low amounts of wear.Questions/purposesWhat is the amount and direction of wear at 5xa0years using radiostereometric analysis (RSA) in patients who had THAs that included second-generation XLPE?MethodsWe prospectively reviewed 21 patients who underwent primary cementless THA with the same design of XLPE acetabular liner and 32-mm articulation. Tantalum markers were inserted during surgery and all patients had RSA radiographs at 1xa0week, 6xa0months, and 1, 2, and 5xa0years postoperatively. Femoral head penetration within the acetabular component was measured with UmRSA® software. One patient died and two had incomplete radiographs leaving 18 radiographic series for analysis.ResultsThe mean amounts of proximal, two-dimensional, and three-dimensional head penetration between 1xa0week and 5xa0years were 0.018, 0.071, and 0.149xa0mm, respectively. The mean proximal, two-dimensional, and three-dimensional wear rates calculated between 1xa0year and 5xa0years were all less than 0.001xa0mm/year with no patient recording a wear rate of more than 0.040xa0mm/year.ConclusionsThe head penetration of a second-generation XLPE liner remained low at 5xa0years and the wear rate calculated after the first year was low in all directions. This low level of wear remains encouraging for the future clinical performance of this material.Level of EvidenceLevel IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

The 6-Year Migration Characteristics of a Hydroxyapatite-Coated Femoral Stem A Radiostereometric Analysis Study

A prospective cohort of 30 patients undergoing primary total hip arthroplasty for treatment of osteoarthritis was enrolled in a study to characterize the migration behavior of a clinically successful cementless stem. At 6 years, the mean subsidence of the stem was 0.63 mm (range, -0.33 to 3.68 mm); the mean rotation into retroversion was 1.41° (range, -1.33° to 7.48°). No stems had additional subsidence of more than 0.25 mm between 6 months and 6 years. The resultant mean subsidence between 2 and 6 years was 0.03 mm, which is below the limit measurable by radiostereometric analysis. The data demonstrate that subsidence of this cementless stem occurs within the first 6 months, after which there is persistent stabilization.

Reintervention after Mobile-bearing Oxford Unicompartmental Knee Arthroplasty

Background Medial compartment osteoarthritis is a common disorder that often is treated by unicompartmental knee arthroplasty (UKA). Although the Oxford 3 prosthesis is commonly used based on revision rate and cumulative survival, our experience suggests that although there may be adequate implant survival rates, we observed a worrisome and undisclosed reintervention rate of nonrevision procedures.Purpose We describe the frequency and cause of repeat intervention subsequent to implanting this device.Methods Between 1998 and 2005, 398 patients underwent UKA using the Oxford 3 prosthesis. The minimum followup was 12xa0months (mean, 43xa0months; range, 12–102xa0months).Results Forty of the 398 (10%) patients had 55 (13.8%) repeat anesthetics (reintervention). There were 38 nonrevision reinterventions. Revision was performed in 15 patients (3.8%), but two patients had a second revision (17 revisions or 4.3%). We revised the UKA to a second UKA in seven of the 15 cases but two subsequently were rerevised to a TKA; eight were revised directly to a TKA.ConclusionsAlthough our data confirm the reported revision rates for this prosthesis, we observed a substantial reintervention rate. Most of the reinterventions are minor and are diagnosed frequently and treated arthroscopically. If revision is required, a second UKA may be considered and performed successfully in patients with isolated loosening of one component.Level of Evidence Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Human immunodeficiency virus infection of human bone derived cells

Human immunodeficiency virus infection of a human bone derived cell line was initiated by either cell free virus or with a cell to cell transmission method. The human bone derived cells were examined for 8 weeks, and virus infection was not detected when assessed by microscopy, immunofluorescence, reverse transcriptase activity, or infection of coculativated human T lymphoid cells susceptible to human immunodeficiency virus. Polymerase chain reaction analysis of human bone derived cells inoculated with the cell to cell infection format showed less than 0.1% infected cells. It is possible that the infected cells detected by polymerase chain reaction were lymphocytes used in the cell to cell infection format. Alternatively, latent infection may have been established in the bone derived cells with no apparent expression of the proviral genome. A large proportion of bone is represented by human bone derived cells, and it is unlikely that bone will contribute to a significant human immunodeficiency virus reservoir in vivo. The blood of bone allograft donors is likely to have a greater virus bioburden than is bone. Methods to sterilize bone should be assessed by their efficacy to inactivate the virus in blood contaminating the graft, and methods to detect human immunodeficiency virus deoxyribonucleic acid in a bone graft may be less sensitive than examining the donors blood.

Detection of periprosthetic osteolysis around total knee arthroplasties an in vitro study.

Periprosthetic osteolysis is a common cause of revision of total knee arthroplasties (TKAs), with plain anteroposterior and lateral (APL) radiographs being the most common method for screening. The aim of this study was to examine the utility of lesion detection and volume appreciation with APL, paired oblique radiographs, and computed tomography. Defects of different sizes were created in 3 cadaveric knees with a cementless TKA in situ and imaged with APL, oblique, and computed tomography modalities. The resultant images were then shown to 3 arthroplasty surgeons, and the absence or presence of lesions, volume size, and confidence in assessment were recorded. The results suggest that the current practice of APL is inferior for the assessment of periprosthetic osteolysis around TKA.

MULTIPARAMETER QUANTITATIVE COMPUTER-ASSISTED TOMOGRAPHY ASSESSMENT OF UNICOMPARTMENTAL KNEE ARTHROPLASTIES

Background:u2003 Unicompartmental knee arthroplasty is a popular alternative to total knee replacement in selected patients. Component alignment has not yet been described by computer‐assisted tomography (CAT) imaging techniques; these have been developed for total knee arthroplasty analysis. The aims of this study were to report two new technologies; a new unicompartmental knee arthroplasty system was radiographically assessed with a new CAT scan protocol.