This study reports on the first 150 consecutive Oxford cementless unicompartmental knee arthroplasties (UKA) performed in an independent centre (126 patients). All eligible patients had functional scores (Oxford knee score and high activity arthroplasty score) recorded pre-operatively and at two- and five-years of follow-up. Fluoroscopically aligned radiographs were taken at five years and analysed for any evidence of radiolucent lines (RLLs), subsidence or loosening. The mean age of the cohort was 63.6 years (39 to 86) with 81 (53.1%) males. Excellent functional scores were maintained at five years and there were no progressive RLLs demonstrated on radiographs. Two patients underwent revision to a total knee arthroplasty giving a revision rate of 0.23/100 (95% confidence interval 0.03 to 0.84) component years with overall component survivorship of 98.7% at five years. There were a further four patients who underwent further surgery on the same knee, two underwent bearing exchanges for dislocation and two underwent lateral UKAs for disease progression. This was a marked improvement from other UKAs reported in New Zealand Joint Registry data and supports the designing centre’s early results.

Cite this article: Bone Joint J 2015;97-B:1358–63.

Objectives

Our study aimed to examine not only the incidence but also the impact of noise from two types of total hip replacement articulations: ceramic-on-ceramic and ceramic-on-polyethylene.

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.

Method.

We prospectively investigated the radiological outcomes of the uncemented Oxford medial compartment arthroplasty in 231 consecutive patients performed in a single centre with a minimum two year follow up.

Objectives

Our study aimed to examine if a mobile-bearing total knee replacement (TKR) offered an advantage over fixed-bearing designs with respect to rates of secondary resurfacing of the patella in knees in which it was initially left unresurfaced.

Bone mineral density (BMD) and bone mineral content (BMC) have not been previously assessed in unicompartmental knee replacement (UKR). We studied the early bone changes beneath the uncemented Oxford medial UKR. Our hypothesis was that this implant should decrease the shear stresses across the bone-implant interface and result in improved BMD and BMC beneath the tibial component.

Using the Lunar iDXA and knee specific software we developed 7 regions of interest (ROI) in the proximal tibia and assessed 38 patients with an uncemented Oxford UKR at 2 years. We measured the replaced knee and contralateral unreplaced knee using the same ROI and compared the BMD and BMC. The initial precision study in 20 patients demonstrated high precision in all areas.

There were 12 males and 16 females with an average age of 65.8 years (46–84 years). ROI 1 and 2 were beneath the tibial tray and had significantly less BMC (p=0.023 and 0.001) and BMD (p=0.012 and 0.002). ROI 3 was the lateral tibial plateau and this area also had significantly less BMC (p=0.007) and BMD (p=0.0001). ROI 4 and 5 immediately below the tibial keel had no significant change. These changes were independent of gender and age.

These results were surprising in that the universal loss of BMC and BMD suggested that bone loading of the proximal tibia was not improved even after a UKR. The better BMD and BMC adjacent to the keel confirms other studies that show improved bone in-growth around keels and pegs in the uncemented tibial component. A prospective longitudinal study has been developed to compare BMD and BMC changes over time to see whether these changes are dynamic.

Developmental dysplasia of the hip (DDH) may lead to premature degenerative arthritis requiring total hip arthroplasty (THA). There is general concern that THA survival in DDH is inferior to that of the general population. We have investigated the results of primary THA performed in patients with DDH in New Zealand.

Through the New Zealand Joint Registry we identified all patients with DDH undergoing primary THA (n = 1205) and all patients with primary osteoarthritis (OA) undergoing primary THA (n = 40589) between 1 January 1999 and 31 December 2008. Postoperative outcomes (including six month Oxford Hip Score (OHS), revision rate, and six month mortality) were analysed and compared between the DDH and the OA groups. Baseline information and operative characteristics were also compared between the two patient groups.

There was no statistically significant difference in six month OHS between the DDH and OA groups from the uncorrected comparison (mean 41.5 vs. 40.8, p=0.056) and from the comparison corrected for known confounding variables (p=0.54). There was no statistically significant difference in revision rate between the DDH and OA groups from the uncorrected comparison (0.79 vs. 0.61 revisions per 100 component years, p=0.121) and from the comparison corrected for known confounding variables (p=0.674). There was no statistically significant difference in six month mortality between the DDH and OA groups from the uncorrected comparison (0.5% vs. 0.8%, p=0.284), however the corrected comparison identified a higher mortality rate in the DDH group (p=0.016).

The DDH group was significantly younger (49.3 years vs. 67.6 years, p<0.001), more often female (74% vs. 52%, p<0.001) and had a lower ASA class (p<0.001) than the OA group. The right hip was involved most often (51% DDH, 54% OA, p=0.03). Bone grafting (4% vs. 0.9%, p<0.001) and uncemented implants (68.3% vs. 28.1%, p<0.001) were more common in the DDH group. Surgical approach did not differ substantially between groups. The DDH group required a longer operative time than the OA group (mean 94.4 minutes vs. 79.7 minutes, p<0.001).

THA in patients with DDH patients is demanding. Despite the complexities inherent to THA in these patients, comparable functional outcomes and revision rates to patients with OA can be expected. Our results supports THA as a successful surgical option for the management of degenerative hip arthritis in patients with DDH.

We carried out a prospective investigation into the radiological outcomes of uncemented Oxford medial compartment unicondylar replacement in 220 consecutive patients (231 knees) performed in a single centre with a minimum two-year follow-up. The functional outcomes using the mean Oxford knee score and the mean high-activity arthroplasty score were significantly improved over the pre-operative scores (p < 0.001). There were 196 patients with a two-year radiological examination performed under fluoroscopic guidance, aiming to provide images acceptable for analysis of the bone–implant interface. Of the six tibial zones examined on each knee on the anteroposterior radiograph, only three had a partial radiolucent line. All were in the medial aspect of the tibial base plate (zone 1) and all measured < 1 mm. All of these patients were asymptomatic. There were no radiolucent lines seen around the femoral component or on the lateral view. There was one revision for loosening at one year due to initial inadequate seating of the tibial component. These results confirm that the early uncemented Oxford medial unicompartmental compartmental knee replacements were reliable and the incidence of radiolucent lines was significantly decreased compared with the reported results of cemented versions of this implant. These independent results confirm those of the designing centre.

The purpose of this study was to investigate the surgical options for unicompartmental osteoarthritis (OA) in younger patients by comparing the survivorship and functional results of Total Knee Replacement (TKR) following osteotomy with the results for both primary TKR and revision of Unicompartmental Knee Replacement (UKR) to a TKR, and thereby recommend the most appropriate index procedure for this group of patients.

We reviewed the revision rate and functional outcome of all patients who had a total knee replacement (TKR) following an osteotomy or Unicompartmental Knee Replacement (UKR) on the New Zealand Joint Registry. We used this data to compare the results to primary TKR scores, including comparison of age-matched subgroups.

There were 711 patients who had undergone TKR as salvage for a failed osteotomy with a revision rate of 1.33 revisions per 100 component years and a mean Oxford knee score (OKS) of 36.9. 205 patients had failed UKR converted to TKR with a revision rate of 1.97 revisions per 100 component years and a mean OKS of 29.1. The revision scores of TKR for both failed osteotomy and failed UKR were significantly poorer than following primary TKR (p← 0.05). The mean OKS following revision of a UKR was significantly poorer than both primary TKR (p←0.001) and TKR for a failed osteotomy (p←0.001). There was no significant difference in mean OKS between primary TKR and TKR for a failed osteotomy, even amongst patients younger than 65 years (p=0.8).

This study has shown that if a surgeon is choosing between an osteotomy and a UKR in the younger patient than the better for any subsequent revision procedure will be achieved with an osteotomy. Revision of a failed osteotomy to a TKR has improved functional results compared to revision of a failed UKR. However, both yield poor survivorship rate compared to primary TKR.

This study reviewed the revision rate of fully cemented, hybrid and cementless primary total knee replacements (TKR) registered in the New Zealand Joint Registry from 1999 to May 2008 to determine whether there was any significant difference in the survival and reason for revision with these different types of fixation.

The percentage rate of revision was calculated per 100 person years (HPY) and compared to the reason for revision, type of fixation and the patient’s age.

Of the 28707 primary TKR registered, 522 underwent revision procedures requiring change of at least one component with a survival rate of 0.44 HPY (1.8%). The majority of revisions were for pain (153) followed by deep infection (133) followed by loosening of the tibial component (98). Overall the rate of tibial loosening was 0.07 HPY (0.3 %) in the cemented group vs 0.25 HPY (1%) in the cementless group (p < 0.001). There was no significant difference in the type of fixation used for the femoral component, but there was a significant difference in the different types of fixation when revised for pain, with the uncemented tibia performing the poorest. There was no significantly difference in the younger patient (< 55 years) with respect to tibial loosening (p=0.92).

Failure of the uncemented total knee replacement was due to pain and tibial loosening although the results in patients under 55 years were similar in all fixation groups. There was no difference in the fixation method of the femoral component.

We have investigated whether the use of laminar-flow theatres and space suits reduced the rate of revision for early deep infection after total hip (THR) and knee (TKR) replacement by reviewing the results of the New Zealand Joint Registry at ten years.

Of the 51 485 primary THRs and 36 826 primary TKRs analysed, laminar-flow theatres were used in 35.5% and space suits in 23.5%. For THR there was a significant increase in early infection in those procedures performed with the use of a space suit compared with those without (p < 0.0001), in those carried out in a laminar-flow theatre compared with a conventional theatre (p < 0.003) and in those undertaken in a laminar-flow theatre with a space suit (p < 0.001) when compared with conventional theatres without such a suit. The results were similar for TKR with the use of a space suit (p < 0.001), in laminar-flow theatres (p < 0.019) and when space suits were used in those theatres (p < 0.001). These findings were independent of age, disease and operating time and were unchanged when the surgeons and hospital were analysed individually.

The rate of revision for early deep infection has not been reduced by using laminar flow and space suits. Our results question the rationale for their increasing use in routine joint replacement, where the added cost to the health system seems to be unjustified.

We reviewed the rate of revision of unicompartmental knee replacements (UKR) from the New Zealand Joint Registry between 1999 and 2008. There were 4284 UKRs, of which 236 required revision, 205 to a total knee replacement (U2T) and 31 to a further unicompartmental knee replacement (U2U). We used these data to establish whether the survival and functional outcome for revised UKRs were comparable with those of primary total knee replacement (TKR). The rate of revision for the U2T cohort was four times higher than that for a primary TKR (1.97 vs 0.48; p < 0.05). The mean Oxford Knee Score was also significantly worse in the U2T group than that of the primary TKR group (30.02 vs 37.16; p < 0.01). The rate of revision for conversion of a failed UKR to a further UKR (U2U cohort) was 13 times higher than that for a primary TKR.

The poor outcome of a UKR converted to a primary TKR compared with a primary TKR should contra-indicate the use of a UKR as a more conservative procedure in the younger patient.

To ascertain whether there is any relationship between the Oxford 12 scores gained six months post surgery and early revision for primary hip and knee arthroplasty.

The six month post surgery Oxford 12 scores were retrieved from the National Joint Registry (NJR) for the seven year period ending 31^st December 2006. These were analysed in relation to revision of primary hip and knee procedures using three methods of statistical analysis; logistic regression, receiver operating characteristic (ROC) curve and direct plotting of groups of scores against the proportion of hips revised for that same group.

Logistic regression: For every one unit increase in the Oxford score there was an 11% increased risk of revision (hips) and 12% (knees) within the first two years of surgery, 5 and 6% respectively between two and four years and 3 and 4% risk respectively between four and six years (p> 0.001).

The ROC Curve Analysis: demonstrated that a patient with a score greater than 20 (hips) or 28.5 (knees) or 24 (uni knees) has eight times the risk of needing a revision within two years compared to a person with a score equal or less than the above numbers. Alternatively the ROC analysis predicted 73% of the revisions within three years for all three arthroplasty groups.

Plotting Scores Against Revisions: Plotting scores in groups of five demonstrated an incremental increase in the risk during the first two years. A person with a score greater than 40 has; for hips 24 times, knees 27 times and uni knees 69 times the risk of a revision within two years compared to a person with a score between 16 and 20.

Monitoring of the six month post surgical Oxford 12 score is another tool in the surgeon’s armamentarium for deciding which patients need closer monitoring following arthroplasty surgery.

Lumbar discectomy is now the operation of choice for lumbosacral radicular syndrome. Few studies of high quality have been performed on the post surgical management of these cases. The studies that have been reported compare one exercise regime to another.

The aim of this study was to compare long term outcomes of usual surgical advice, involving no formal post-surgical rehabilitation, with a non-aggravating six month gym rehabilitation programme post lumbar discectomy. This study is a prospective randomised controlled trial using a cohort followed for three years.

The patients were computer randomised into two groups. Group A, the control group followed usual surgical advice which was to resume normal activity as soon as pain allowed. Group B, undertook the gym rehabilitation programme. Inclusion criteria were: age 17 to 65 years, good health and no major medical problems. The surgical level had to be L3, L4, or L5. Patients were excluded if they had central neurological disorders, communication difficulties, any condition making gym-based exercises unsafe, or if the surgery was indicated for spinal infection, tumour or inflammatory disease. Patients were followed for a three year period using validated outcome measures (Roland-Morris Questionnaire and Oswestry Low Back Pain Index) and an annual Quality of Life (QoL) questionnaire. The annual questionnaire reported information on number of GP visits, other therapist visits, medication levels and time off work.

Ninety three participants were randomised; Control n=46 and trial n=47. Eighty nine participants completed the study. Randomisation achieved a balance of confounding factors, with the exception of work heaviness, where there were a greater number of participants in the very heavy and heavy categories in the trial group (P< 0.01). Functional outcome measures did not achieve statistical difference over the three year period. Other studies have shown these measures to be reliable for short term follow up but their reliability diminishes with time (1,2). Key findings of cumulative three year data for the QoL questionnaire were in the intent-to-treat analysis: fewer GP visits in the trial group p< 0.008; and per protocol: fewer episodes off work p< 0.01 (49% versus 15%), fewer days off p< 0.053 and fewer GP visits p< 0.009.

The results reveal an advantage in terms of episodes off work and GP visits for participants in Group B who completed the programme. Time off work is a significant consideration for funding providers. These results suggest that surgeons should consider referral of discectomy patients to appropriate post-surgical rehabilitation programmes.

We have reviewed the rate of revision of fully cemented, hybrid and uncemented primary total hip replacements (THRs) registered in the New Zealand Joint Registry between 1999 and December 2006 to determine whether there was any statistically significant difference in the early survival and reason for revision in these different types of fixation. The percentage rate of revision was calculated per 100 component years and compared with the reason for revision, the type of fixation and the age of the patients.

Of the 42 665 primary THRs registered, 920 (2.16%) underwent revision requiring change of at least one component. Fully-cemented THRs had a lower rate of revision when considering all causes for failure (p < 0.001), but below the age of 65 years uncemented THRs had a lower rate (p < 0.01). The rate of revision of the acetabular component for aseptic loosening was less in the uncemented and hybrid groups compared with that in the fully cemented group (p < 0.001), and the rate of revision of cemented and uncemented femoral components was similar, except in patients over 75 years of age in whom revision of cemented femoral components was significantly less frequent (p < 0.02). Revision for infection was more common in patients aged below 65 years and in cemented and hybrid THRs compared with cementless THRs (p < 0.001). Dislocation was the most common cause of revision for all types of fixation and was more frequent in both uncemented acetabular groups (p < 0.001). The experience of the surgeon did not affect the findings.

Although cemented THR had the lowest rate of revision for all causes in the short term (90 days), uncemented THR had the lowest rate of aseptic loosening in patients under 65 years of age and had rates comparable with international rates of aseptic loosening in those over 65 years.

We have examined the outcome of 400 consecutive patients who underwent total knee replacement with the Low Contact Stress mobile-bearing system between 1993 and 1994 and were followed up for a minimum of ten years. All operations were performed by surgeons in Christchurch, New Zealand, who used no other knee prosthesis during the study time.

At ten years after operation 238 patients (244 knees) remained for independent clinical and radiological assessment. There was a significant improvement (p < 0.001) in the postoperative knee scores at one, three, seven and ten years, although a slight deterioration in the score occurred between seven and ten years which did not reach statistical significance. The survival for polyethylene wear or loosening was 97% (95% CI 96 to 98) and survival using reoperation for any cause was 92% (95% CI 90 to 94) at 12 years. Polyethylene wear was more common in the meniscal-bearing component, with five knees requiring revision and a further eight demonstrating early wear. Osteolysis was not seen in the rotating platform component, but was present in three of the meniscal-bearing knees.

There was no association between the radiological alignment at one year and those knees that subsequently required revision. However, there was an association between the overall limb alignment and the Western Ontario McMasters University score (p < 0.001).

The Low Contact Stress mobile-bearing total knee replacement has proved to be a reliable implant at ten years when used in primary knee replacement irrespective of the deformity and diagnosis.

Lumbar discectomy is now the operation of choice for lumbosacral radicular syndrome. Few studies of high quality have been performed on the post surgical management of these cases. The studies that have been reported compared one exercise regime to another. This study compares an exercise group with a true control group involving no exercise or formal rehabilitation. This is a randomized controlled trial comparing post surgical lumbar discectomy management regimes.

Ninety three lumbar discectomy patients were randomized to two groups. Group A; the control group followed usual surgical advice which was to resume normal activity as soon as pain allowed. Group B; undertook a six month supervised non aggravating gym rehab programme. Both groups were followed for a one year period using validated outcome measures and a questionnaire. The results are based on an intention-to-treat analysis.

Patients in both groups improved during the one year follow up period (P=0.001). However there was no statistical difference between groups at the clinical end point (Roland Morris P=0.83, Oswestry Low back index P=0.90). Group B patients returned to work seven days earlier than group A patients and had fewer days off work in the one year follow up period but this difference was not statistically significant.

There was no statistical advantage gained by the patients who performed the gym rehabilitation programme after one year follow up. These are the preliminary one year results of a three year follow up study.

Introduction Lumbar discectomy is now the operation of choice for lumbosacral radicular syndrome. Few studies of high quality have been performed on the post-surgical management of these cases (Ostelo RWJG, et al; Spine 2003). The studies that have been reported compared one exercise regime to another. This study compares an exercise group with a true control group involving no exercise or formal rehabilitation. This is a randomised controlled trial comparing post surgical lumbar discectomy management regimes.

Methods Ninety-three lumbar discectomy patients were randomised to two groups. Group A; the control group followed usual surgical advice which was to resume normal activity as soon as pain allowed. Group B; undertook a six month supervised non- aggravating gym rehab programme. Both groups were followed for a one year period using validated outcome measures and questionnaires (Roland Morris, Oswestry Low-back Score). The results are based on an intention-to-treat analysis.

Results Patients in both groups improved during the one-year follow-up period (P=0.001). However there was no statistical difference between groups at the clinical end point (Roland Morris P=0.83, Oswestry Low-back Index P=0.90). Group B patients returned to work seven days earlier than group A patients and had fewer days off work in the one year follow-up period but this difference was not statistically significant.

Discussion There was no statistical advantage gained by the patients who performed the gym rehabilitation programme after one year follow-up. These are the preliminary one-year results of a three-year follow-up study.

We have studied the incidence of tumours at remote sites following total hip replacement: 1,358 individuals have been followed up for 14,286 person-years after operation. In the decade following implantation the incidence of tumours of the lymphatic and haemopoietic systems was significantly greater, and that of cancer of the breast, colon, and rectum, significantly less than expected. Whilst the association might be due in part to an effect of the prosthetic implants, other mechanisms, particularly drug therapy, require consideration.