We randomised 62 knees to receive either cemented or cementless versions of the Oxford unicompartmental knee replacement. The implants used in both arms of the study were similar, except that the cementless components were coated with porous titanium and hydroxyapatite. The tibial interfaces were studied with fluoroscopically-aligned radiographs.

At one year there was no difference in clinical outcome between the two groups. Narrow radiolucent lines were seen at the bone-implant interfaces in 75% of cemented tibial components. These were partial in 43%, and complete in 32%. In the cementless implants, partial radiolucencies were seen in 7% and complete radiolucencies in none. These differences are statistically significant (p < 0.0001) and imply satisfactory bone ingrowth into the cementless implants.

We studied the bone mineral density (BMD) and the bone mineral content (BMC) of the proximal tibia in patients with a well-functioning uncemented Oxford medial compartment arthroplasty using the Lunar iDXA bone densitometer. Our hypothesis was that there would be decreased BMD and BMC adjacent to the tibial base plate and increased BMD and BMC at the tip of the keel.

There were 79 consecutive patients (33 men, 46 women) with a mean age of 65 years (44 to 84) with a minimum two-year follow-up (mean 2.6 years (2.0 to 5.0)) after unilateral arthroplasty, who were scanned using a validated standard protocol where seven regions of interest (ROI) were examined and compared with the contralateral normal knee. All had well-functioning knees with a mean Oxford knee score of 43 (14 to 48) and mean Knee Society function score of 90 (20 to 100), showing a correlation with the increasing scores and higher BMC and BMD values in ROI 2 in the non-implanted knee relative to the implanted knee (p = 0.013 and p = 0.015, respectively).

The absolute and percentage changes in BMD and BMC were decreased in all ROIs in the implanted knee compared with the non-implanted knee, but this did not reach statistical significance. Bone loss was markedly less than reported losses with total knee replacement.

There was no significant association with side, although there was a tendency for the BMC to decrease with age in men. The BMC was less in the implanted side relative to the non-implanted side in men compared with women in ROI 2 (p = 0.027), ROI 3 (p = 0.049) and ROI 4 (p = 0.029).

The uncemented Oxford medial compartment arthroplasty appears to allow relative preservation of the BMC and BMD of the proximal tibia, suggesting that the implant acts more physiologically than total knee replacement. Peri-prosthetic bone loss is an important factor in assessing long-term implant stability and survival, and the results of this study are encouraging for the long-term outcome of this arthroplasty.

Cite this article: Bone Joint J 2013;95-B:1480–3.

We audited the relationship between obesity and the age at which hip and knee replacement was undertaken at our centre. The database was analysed for age, the Oxford hip or knee score and the body mass index (BMI) at the time of surgery. In total, 1369 patients were studied, 1025 treated by hip replacement and 344 by knee replacement. The patients were divided into five groups based on their BMI (normal, overweight, moderately obese, severely obese and morbidly obese).

The difference in the mean Oxford score at surgery was not statistically significant between the groups (p > 0.05). For those undergoing hip replacement, the mean age of the morbidly obese patients was ten years less than that of those with a normal BMI. For those treated by knee replacement, the difference was 13 years. The age at surgery fell significantly for those with a BMI > 35 kg/m² for both hip and knee replacement (p > 0.05). This association was stronger for patients treated by knee than by hip replacement.

The low contact stress patellofemoral replacement consists of a trochlear component and a modular patellar component which has a metal-backed mobile polyethylene bearing. We present the early results of the use of this prosthesis for established isolated patellofemoral arthritis in 51 consecutive patellofemoral replacements in 35 patients. The mean follow-up was 25 months (5 to 60). The estimated survival rate at three years was 63% (95% confidence interval 47 to 80) with revision as the endpoint and 46% (95% confidence interval 30 to 63) with revision and ongoing moderate or severe pain as the endpoint.

The early results of the use of the low contact stress patellofemoral replacement are disappointing with a high rate of revision. We cannot therefore recommend its use.

The October 2013 Knee Roundup³⁶⁰ looks at: Make it easy, release the MCL; Do patients remember clinical information in day surgery?; Osteoarthritis and arthroscopy?; How best to double your bundles; When to operate for infection; Cementless unicompartment knee replacement?; Tibial tubercle-trochlear groove confusion; Tarts, cherries and osteoarthritis

The Oxford unicompartmental knee replacement (UKR) was designed to minimise wear utilising a fully-congruent, mobile, polyethylene bearing. Wear of polyethylene is a significant cause of revision surgery in UKR in the first decade, and the incidence increases in the second decade. Our study used model-based radiostereometric analysis to measure the combined wear of the upper and lower bearing surfaces in 13 medial-compartment Oxford UKRs at a mean of 20.9 years (17.2 to 25.9) post-operatively.

The mean linear penetration of the polyethylene bearing was 1.04 mm (0.307 to 2.15), with a mean annual wear rate of 0.045 mm/year (0.016 to 0.099). The annual wear rate of the phase-2 bearings (mean 0.022 mm/year) was significantly less (p = 0.01) than that of phase-1 bearings (mean 0.07 mm/year).

The linear wear rate of the Oxford UKR remains very low into the third decade. We believe that phase-2 bearings had lower wear rates than phase-1 implants because of the improved bearing design and surgical technique which decreased the incidence of impingement. We conclude that the design of the Oxford UKR gives low rates of wear in the long term.

The strain on clinic and surgeon resources resulting from a rise in demand for total knee replacement (TKR) requires reconsideration of when and how often patients need to be seen for follow-up. Surgeons will otherwise require increased paramedical staff or need to limit the number of TKRs they undertake. We reviewed the outcome data of 16 414 primary TKRs undertaken at our centre to determine the time to re-operation for any reason and for specific failure mechanisms. Peak risk years for failure were determined by comparing the conditional probability of failure, the number of failures divided by the total number of TKRs cases, for each year. The median times to failure for the most common failure mechanisms were 4.9 years (interquartile range (IQR) 1.7 to 10.7) for femoral and tibial loosening, 1.9 years (IQR 0.8 to 3.9) for infection, 3.1 years (IQR 1.6 to 5.5) for tibial collapse and 5.6 years (IQR 3.4 to 9.3) for instability. The median time to failure for all revisions was 3.3 years (IQR 1.2 to 8.5), with an overall revision rate of 1.7% (n = 282). Results from our patient population suggest that patients be seen for follow-up at six months, one year, three years, eight years, 12 years, and every five years thereafter. Patients with higher pain in the early post-operative period or high body mass index (≥ 41 kg/m²) should be monitored more closely.

Cite this article: Bone Joint J 2013;95-B:1484–9.

We have reviewed 22 patients at a mean of 30 years (28 to 31) after a whiplash injury. A complete recovery had been made in ten (45.5%) while one continued to describe severe symptoms. Persistent disability was associated with psychological distress but both improved in the period between 15 and 30 years after injury. After 30 years, ten patients (45.5%) were more disabled by knee than by neck pain.

We evaluated the clinical results and complications after extra-articular resection of the distal femur and/or proximal tibia and reconstruction with a tumour endoprosthesis (MUTARS) in 59 patients (mean age 33 years (11 to 74)) with malignant bone or soft-tissue tumours. According to a Kaplan–Meier analysis, limb survival was 76% (95% confidence interval (CI) 64.1 to 88.5) after a mean follow-up of 4.7 years (one month to 17 years). Peri-prosthetic infection was the most common indication for subsequent amputation (eight patients). Survival of the prosthesis without revision was 48% (95% CI 34.8 to 62.0) at two years and 25% (95% CI 11.1 to 39.9) at five years post-operatively. Failure of the prosthesis was due to deep infection in 22 patients (37%), aseptic loosening in ten patients (17%), and peri-prosthetic fracture in six patients (10%). Wear of the bearings made a minor revision necessary in 12 patients (20%). The mean Musculoskeletal Tumor Society score was 23 (10 to 29). An extensor lag > 10° was noted in ten patients (17%).

These results suggest that limb salvage after extra-articular resection with a tumour prosthesis can achieve good functional results in most patients, although the rates of complications and subsequent amputation are higher than in patients treated with intra-articular resection.

Cite this article: Bone Joint J 2013;95-B:1425–31.

The June 2013 Knee Roundup³⁶⁰ looks at: knee arthroplasty in diabetic patients; whether TKR is a timebomb; the use of antidepressants for knee OA; trochleoplasty; articulated spacers; mental health and joint replacement; and the use of physiotherapy for meniscal tear.

The Oxford hip and knee scores have been extensively used since they were first described in 1996 and 1998. During this time, they have been modified and used for many different purposes. This paper describes how they should be used and seeks to clarify areas of confusion.

The aim of this study was to review the early outcome of the Femoro-Patella Vialla (FPV) joint replacement. A total of 48 consecutive FPVs were implanted between December 2007 and June 2011. Case-note analysis was performed to evaluate the indications, operative histology, operative findings, post-operative complications and reasons for revision. The mean age of the patients was 63.3 years (48.2 to 81.0) and the mean follow-up was 25.0 months (6.1 to 48.9). Revision was performed in seven (14.6%) at a mean of 21.7 months, and there was one re-revision. Persistent pain was observed in three further patients who remain unrevised. The reasons for revision were pain due to progressive tibiofemoral disease in five, inflammatory arthritis in one, and patellar fracture following trauma in one. No failures were related to the implant or the technique. Trochlear dysplasia was associated with a significantly lower rate of revision (5.9% vs 35.7%, p = 0.017) and a lower incidence of revision or persistent pain (11.8% vs 42.9%, p = 0.045).

Focal patellofemoral osteoarthritis secondary to trochlear dysplasia should be considered the best indication for patellofemoral replacement. Standardised radiological imaging, with MRI to exclude overt tibiofemoral disease should be part of the pre-operative assessment, especially for the non-dysplastic knee.

Cite this article: Bone Joint J 2013;95-B:793–7.

Pre-operative variables are increasingly being used to determine eligibility for total knee replacement (TKR). This study was undertaken to evaluate the relationships, interactions and predictive capacity of variables available pre- and post-operatively on patient satisfaction following TKR. Using nationally collected patient reported outcome measures and data from the National Joint Registry for England and Wales, we identified 22 798 patients who underwent TKR for osteoarthritis between August 2008 and September 2010. The ability of specific covariates to predict satisfaction was assessed using ordinal logistic regression and structural equational modelling. Only 4959 (22%) of 22 278 patients rated the results of their TKR as ‘excellent’, despite the majority (71%, n = 15 882) perceiving their knee symptoms to be much improved. The strongest predictors of satisfaction were post-operative variables. Satisfaction was significantly and positively related to the perception of symptom improvement (operative success) and the post-operative EuroQol-5D score. While also significant within the models pre-operative variables were less important and had a minimal influence upon post-operative satisfaction. The most robust predictions of satisfaction occurred only when both pre- and post-operative variables were considered together. These findings question the appropriateness of restricting access to care based on arbitrary pre-operative thresholds as these factors have little bearing on post-operative satisfaction.

Cite this article: Bone Joint J 2013;95-B:1359–65.

We report the results of revision total knee replacement (TKR) in 26 patients with major metaphyseal osteolytic defects using 29 trabecular metal cones in conjunction with a rotating hinged total knee prosthesis. The osteolytic defects were types II and III (A or B) according to the Anderson Orthopaedic Research Institute (AORI) classification. The mean age of the patients was 72 years (62 to 84) and there were 15 men and 11 women. In this series patients had undergone a mean of 2.34 previous total knee arthroplasties. The main objective was to restore anatomy along with stability and function of the knee joint to allow immediate full weight-bearing and active knee movement. Outcomes were measured using Knee Society scores, Oxford knee scores, range of movement of the knee and serial radiographs. Patients were followed for a mean of 36 months (24 to 49). The mean Oxford knee clinical scores improved from 12.83 (10 to 15) to 35.20 (32 to 38) (p < 0.001) and mean American Knee Society scores improved from 33.24 (13 to 36) to 81.12 (78 to 86) (p < 0.001). No radiolucent lines suggestive of loosening were seen around the trabecular metal cones, and by one year all the radiographs showed good osteo-integration. There was no evidence of any collapse or implant migration. Our early results confirm the findings of others that trabecular metal cones offer a useful way of managing severe bone loss in revision TKR.

Cite this article: Bone Joint J 2013;95-B:1069–74.

We report ten-year clinical and radiological follow-up data for the Sigma Press Fit Condylar total knee replacement system (Sigma PFC TKR). Between October 1998 and October 1999 a total of 235 consecutive PFC Sigma TKRs were carried out in 203 patients. Patients were seen at a specialist nurse-led clinic seven to ten days before admission and at six and 18 months, three, five and eight to ten years after surgery. Data were recorded prospectively at each clinic visit. Radiographs were obtained at the five- and eight- to ten-year follow-up appointments. Of the 203 patients, 147 (171 knees) were alive at ten years and 12 were lost to follow-up. A total of eight knees (3.4%) were revised, five for infection and three to change the polyethylene insert. The survival at ten years with an endpoint of revision for any reason was 95.9%, and with an endpoint of revision for aseptic failure was 98.7%. The mean American Knee Society Score (AKSS) was 79 (10 to 99) at eight to ten years, compared with 31 (2 to 62) pre-operatively. Of 109 knee with radiographs reviewed, 47 knees had radiolucent lines but none showed evidence of loosening.

Cite this article: Bone Joint J 2013;95-B:177–80.

The Morquio syndrome is a rare disorder which presents with a number of musculoskeletal problems. The literature describing total knee replacement in these patients is sparse. We describe the management of a patient with bilateral instability and pain in the knees using bilateral constrained knee replacements, and followed up for five years with pre- and postoperative knee scores. We highlight the difficulties encountered and discuss the end results.

The December 2012 Knee Roundup³⁶⁰ looks at: the demand for knee replacement; a Japanese knee outcome score; smoking and TKR; coronal alignment as a determinant of outcome in TKR; fixed flexion; MRI detected knee lesions; and lateral domed Oxford unicompartmental knee replacements.

The February 2013 Knee Roundup³⁶⁰ looks at: mobile-bearing TKRs; arthroscopic ACL reconstruction; the use of chondrocytes for osteochondral defects; ACL reconstruction and the return to pivoting sports; ACLs and the MOON study; the benefit of knee navigation; and trabecular metal.

Trochlear dysplasia is a developmental condition characterised by an abnormally flat or dome-shaped trochlea and is an important contributory factor to patellofemoral instability and recurrent dislocation. We studied prospectively a series of 54 consecutive patients (59 knees) with patellofemoral instability secondary to trochlear dysplasia, who were treated by a trochleoplasty by a single surgeon between June 2002 and June 2007.

Pre- and post-operative scores were assessed by the patients and a satisfaction questionnaire was completed.

Of the 54 patients (59 knees) in the series, 39 (44 knees) were female and 15 (15 knees) were male. Their mean age at surgery was 21 years and 6 months (14 years 4 months to 33 years 11 months). In 40 patients (42 knees) the mean follow-up was for 24 months (12 to 58). One patient was unable to attend for follow-up. An analysis of the results of those patients followed up for at least 12 months showed a statistically significant improvement in outcome (p < 0.001 for all scores). Overall, 50 patients (92.6%) were satisfied with the outcome of their procedure.

The early results of trochleoplasty are encouraging in this challenging group of patients.