Medium-term survivorship of the Oxford phase 3 unicompartmental knee replacement (UKR) has not yet been established in an Asian population. We prospectively evaluated the outcome of 400 phase 3 Oxford UKRs in 320 Korean patients with a mean age at the time of operation of 69 years (48 to 82). The mean follow-up was 5.2 years (1 to 10). Clinical and radiological assessment was carried out pre- and post-operatively. At five years, the mean Knee Society knee and functional scores had increased significantly from 56.2 (30 to 91) pre-operatively to 87.2 (59 to 98) (p = 0.034) and from 59.2 (30 to 93) to 88.3 (50 to 100) (p = 0.021), respectively. The Oxford knee score increased from a mean of 25.8 (12 to 39) pre-operatively to 39.8 (25 to 58) at five years (p = 0.038). The ten-year survival rate was 94% (95% confidence interval 90.1 to 98.0). A total of 14 UKRs (3.5%) required revision. The most common reason for revision was dislocation of the bearing in 12 (3%). Conversion to a total knee replacement was required in two patients who developed osteoarthritis of the lateral compartment. This is the largest published series of UKR in Korean patients. It shows that the mid-term results after a minimally invasive Oxford phase 3 UKR can yield satisfactory clinical and functional results in this group of patients

Introduction: The use of the Oxford Phase 3 unicompartmental knee arthroplasty (UKA) in the treatment of anteromedial osteoarthritis of the knee in elderly patients is controversial. The aim of this study was to analyse the performance of patients 75 years of age or older after surgery with the Oxford Phase 3 prosthesis by a minimally invasive technique. Material and methods: Between January 1999 and September 2004, 128 Oxford Phase 3 prostheses were implanted by a single surgeon. Patients with a minimal follow up (FU) of one year were divided in two groups depending on age. (Group A less than 75 years, group B 75 years or more.) Loss to FU was documented. The pre and postoperative clinical outcome of the patient with the new implant was objectively evaluated by a visual analog pain and satisfaction score, the WOMAC Score, Oxford score, the Knee Society knee score and Knee Society function score. The range of motion (ROM) was documented. Results: Fourty-five patients were under the age of 75 (group A). Thirty patients were 75 or older (group B). In the second group 4 patients were lost to FU: two deceased and two due to severe illness. Mean age (range) in the first and second group was 67 (47–74 yrs) and 79 (76–87) years respectively. Both groups had a mean FU time of 29 months. In the preoperative scores there was a significant difference in the WOMAC function score (49.7 A vs 42.4 B), Knee Society knee score (51.2 A vs 45.5 B) and the Knee Society function score (51.7 A vs 41.4 B).The pre-operative ROM was 120.1 (A) vs 122.7 (B) degrees. Comparing the postoperative scores a significant difference was found in the Knee Society knee score (89.1 A vs 78.0 B) and in the WOMAC function score (77.8 A vs 74.0 B). The Oxford score and the postoperative VAS for pain and satisfaction were slightly in favour for the younger group, but did not differ significantly. The postoperative ROM was 126 degrees in both groups. Conclusions: This study shows that in both groups the scores are good to excellent but slightly in favour for the younger group of patients operated for anteromedial osteoarthritis using a minimally invasive approach. Patients’ satisfaction is high in both groups. The slight difference in scores may be due to the presence of comorbidity in the older patient. Although the follow up in this study is the shortterm we advocate the use of the Oxford Phase 3 prosthesis in the elderly patient. The minimally invasive technique will lead to better range of movement, a quicker recovery of the older patient with less risk of complications and will be in our opinion more cost-effective than total knee replacement

To identify frequency and patterns of Oxford Phase 3 Unicompartmental Knee Arthroplasty (UKA) failure in New Zealand through analysis of national primary and revision data. Compare the results of this data with that of total knee arthroplasty and other international joint registers. Retrospective audit examining all Oxford Phase 3 UKAs recorded in the New Zealand National Joint Register from January 2000 to December 2007 were analysed and then statistic al analysis performed to identify patterns of failure and reasons for revision. Two thousand six hundred and twenty Oxford UKAs were performed by 99 Orthopædic Surgeons. The average age was 66.1 years (range 35–94). Osteoarthritis was the primary diagnosis. Mean time to revision 839 days (2.3 years). Revision rate was 5.6% (n=148). The most common reasons for revision were pain (n=61, 41%), aseptic loosening (n=53, 36%), and bearing dislocation (n=16, 11%). Deep infection rate was 0.26% (7/2620) compared with 1.76% of total knee arthroplasties (564/32029). Six surgeons (high use & #8805;10 UKAs/year) performed 699 (26.7%) operations, revision rate 2.6%. Fifty-five surgeons (low use & #8804; two UKA/year) performed 283 (10.8%) operations, revision rate 10.6%. There was a statistically significant difference seen with an inverse relationship between surgeon experience and revision. The revision rate for the Oxford is three, two times greater than TKA. UKA is now decreasing in New Zealand whilst Total Knee Arthroplasty (TKA) continues to increase. The number of is now decreasing in New Zealand whilst Total Knee Arthroplasty (TKA) continues to increase. The number of surgeons using Oxford UKA has increased by 19% but the number of Oxfords being done has fallen by 13%. High use surgeons’ revision rate is now higher than TKA. An inverse relationship between failure and surgeon experience exists which confirms Swedish Knee Arthroplasty register reports. The deep infection rate is less than TKA. Revisions were performed early for unexplained pain in the absence of obvious mechanical failure. This is against generally held wisdom for TKA and may reflect the perception that UKA is easily revised to TKA

Objectives: The results of knee arthroplasty are commonly assessed by survival analysis using revision as the endpoint. We have used the assessment of pain by a patient based questionnaire as an alternative after the Oxford Phase 3 UKA implanted by a minimally invasive technique. Materials and Methods: Between January 1999 and May 2007, 223 consecutive Oxford arthroplasties were implanted by a single surgeon in a county hospital. Mean followup period was 35 months. Patients were assessed prospectively pre-operatively and after UKA in each year subsequently by a questionnaire. Survival analysis was undertaken. Results: Preoperatively 85.8% had moderate or severe pain. Postoperatively, of five patients(2.6%) with persisting pain due to failure of using proper patient selection three were revised to TKA and two are still being followed. Three patients(1.6%) with moderate pain after using proper indication criteria accepted their complaints. Ten other patients (5.2%) experiencing moderate pain some time during the eight year period were successfully treated by arthroscopy. If after surgery patients experienced pain which had spontaneous improved by the second year, the initial pain was ignored. Totally 9.6% of patients experienced moderate or severe pain at some stage, and the failure rate was 4.2% in this period of 8 years’ experience. Conclusion: When strict indications are followed the failure rate of the procedure can be minimised till 1.6% when moderate pain is considered the endpoint. As relief of pain is the primary reason for joint replacement, this is likely to be the most important factor in determining the long-term outcome for the patient

To identify frequency and patterns of Oxford Phase 3 UKA failure in New Zealand through analysis of national primary and revision data. Retrospective audit examining all revision Oxford Phase 3 UKAs recorded in the New Zealand National Joint Register from January 2000 to October 2003 were analysed along with surgeons’ clinical notes and patient x-rays. Seventy-three Orthopædic Surgeons performed 1216 Oxford UKAs. The average age was 66.4 years (range 35–94). Osteoarthritis was the primary diagnosis for 1163 (96%) patients. Mean time to revision was 437 days (14.4 months). The early revision rate was 2.2% (n=27). The most common reasons for revision were aseptic loosening (n=7, 26%), bearing dislocation (n=5, 19%) and pain (n=4, 15%). The deep infection rate was 0.16% (2/1216). Eighteen surgeons (high use > 8 UKAs/year) performed 787 (64%) operations, with a revision rate of 1.5%. Twenty-two surgeons (low use ≤ 1 UKA/year) performed 38 (3%) operations, with a revision rate of 8%. This was statistically significant, p= 0.03 (odds ratio 5.7). The early revision rate for the Oxford UKA is 1.4 times greater than TKA. High use surgeons revision rate is lower than TKA. An inverse relationship between failure and surgeon experience exists. This confirms Swedish Knee Arthroplasty Register findings

Introduction: The introduction of the Oxford Phase 3 unicompartmental knee arthroplasty (UKA) by a minimally invasive technique has significantly changed the treatment of medial osteoarthritis of the knee joint. The purpose of this study was to analyse our early results and to evaluate the clinical importance of the learning curve of the procedure. Material and methods: Patients who were operated between January 1999 and September 2003, were divided in two groups. Group A consists of 34 patients (35 prostheses) who were operated between January 1999 and December 2001 with a minimal follow-up (FU) time of 24 months. The second group (B) consists of 41 patients (44 prostheses) who had surgery between January 2002 and September 2003 with a FU of minimal 12 months. WOMAC score, Oxford score, Knee Society knee/function score, VAS for pain and satisfaction, radiographical alignment, operation time and complications were documented and compared between the two groups. A slight modification of the operation technique was applied in the second group. Results: The Knee Society function score differed significantly in favour for group B (81.5 A vs 88.1 B; p< 0.05). The Knee Society knee score was: 86.7 (A) vs 89.7 (B). The postoperative VAS for pain and satisfaction were slightly in favour for the second group. The Oxford and WOMAC score did not differ significantly. The ROM was 125.1 (A) vs 126.7 (B) degrees. The operation time was 84 (A) vs 64 (B) minutes. The radiographical tibio-femoral alignment was 6.1 (A) vs 6.4 (B) valgus. Optimal radiographical positioning of the three components was 51% (18/35;A) vs 80 % (35/44;B). Two complications were encountered only in the first group: dislocation of the meniscal bearing component, and lesion of the lateral meniscus. There were three patients with moderate pain complaints in group A and two in B. Conclusions: This study shows that when an appropriate surgical technique is mastered from the very beginning, good to excellent clinical results can be achieved even in the learning curve period. The positioning of the prosthesis, as confirmed by radiographical study, after using our own modification of the surgical technique was improved

This prospective study describes the outcome of the first 1000 phase 3 Oxford medial unicompartmental knee replacements (UKRs) implanted using a minimally invasive surgical approach for the recommended indications by two surgeons and followed up independently. The mean follow-up was 5.6 years (1 to 11) with 547 knees having a minimum follow-up of five years. At five years their mean Oxford knee score was 41.3 (. sd. 7.2), the mean American Knee Society Objective Score 86.4 (. sd. 13.4), mean American Knee Society Functional Score 86.1 (. sd. 16.6), mean Tegner activity score 2.8 (. sd. 1.1). For the entire cohort, the mean maximum flexion was 130° at the time of final review. The incidence of implant-related re-operations was 2.9%; of these 29 re-operations two were revisions requiring revision knee replacement components with stems and wedges, 17 were conversions to a primary total knee replacement, six were open reductions for dislocation of the bearing, three were secondary lateral UKRs and one was revision of a tibial component. The most common reason for further surgical intervention was progression of arthritis in the lateral compartment (0.9%), followed by dislocation of the bearing (0.6%) and revision for unexplained pain (0.6%). If all implant-related re-operations are considered failures, the ten-year survival rate was 96% (95% confidence interval, 92.5 to 99.5). If only revisions requiring revision components are considered failures the ten-year survival rate is 99.8% (confidence interval 99 to 100). This is the largest published series of UKRs implanted through a minimally invasive surgical approach and with ten-year survival data. The survival rates are similar to those obtained with a standard open approach whereas the function is better. This demonstrates the effectiveness and safety of a minimally invasive surgical approach for implanting the Oxford UKR

Great interest in unicompartmental knee arthroplasty (UKA) for medial osteoarthritis has rapidly increased following the introduction of minimally invasive UKA (MI-UKA). This approach preserves the normal anatomy of knee, causes less damage to extensor mechanism and results in a more rapid post-operative recovery. However, experience with this approach is limited in China. The aim of this report was to determine the short-term clinical and radiographic outcomes of MI-UKA in the Chinese, and to identify any features that are unique to this population. Fifty two knees, in forty-eight patients, with medial compartmental osteoarthritis treated by MI-UKA via C-arm intensifier guide (CAIG) from May 2005 to January 2009 were reviewed. Pain and range of motion (ROM) was assessed using the HSS scoring system before and after surgery. Pre- and postoperative alignment of the lower limbs was measured and compared. The mean follow up time was 24 months (12-42 months). In all cases the pain over medial compartment of the knees was relieved or subsided. The post-operative ROM was 0-136 degree (mean 122degree), and the mean alignment was 2degree varus (0- 7degree varus). The HSS score increased from 72(61-82) to 92(72-95). 93% of the postoperative scores were good or excellent. Interestingly, the distribution of femoral component sizes of these patients was XS 2%, Small 83%, Medium 15%, Large 0%, XL 0%; whereas tibial component size was AA 27%, A 55%, B 15%, C 3%, D 0%, E 0%, and F 0%. The optimal fitted match between tibial and femoral size was: tibia AA and A with XS and small femur, tibia B and C with medium femur. The estimated match was: tibia D and E with large femur, tibia F with XL femur. In contrast to the Oxford report, the sizes of these components are smaller and not in correlation with the height, weight and BMI of the patients. We conclude that MI-UKA is an effective method for treating medial compartmental osteoarthritis of the knee in the Chinese population. CAIG is a feasibly intraoperative measure to predict femoral component sizes. However, component sizes and combinations are different from the Oxford guideline.

Introduction: The introduction of Oxford UKA byminimally invasive techniques has signiþcantly changed the treatment of anteromedial osteoarthritis of the knee joint. It is therefore necessary to evaluate this treatment option both clinically and radiologically. Aims: To study the radiographic and clinical results of the Oxford medial UKA in patients with a minimum follow up of 2 years in a single centre. Methods: A prospective independent study in which 67 consecutive UKAs were implanted by a single surgeon, using a minimally invasive technique. All patients with a minimum follow up of 2 years were pre- and postoperatively clinically evaluated by the AKSS and radiologically according to the Oxford Centre criteria, including ßuoroscopy. Results: Clinical: 28 patients with 30 prostheses (mean FU: 2.54 yr; mean age: 71.4 yrs) were included. The Knee Score improved signiþcantly from 58.7 (pre-op) to 95.0 (FU). The Function Score improved from 54.5 to 88.8. Mean ROM was 125û preoperatively and 121û at FU.Radiological: preop: varus deformity (n=18; mean 3.4û; range 2–10û), and valgus (n=12; 5.4, 2–12û). Postop: valgus alignment in all (n=30; 6.3û, 4–12û). Fifteen cases (50%) showed signs of patellofemoral arthritis (PFA); 11 cases with grade 2–3 PFA had a maximum pain score of 50. Full congruency of the tibial and femoral components was obtained in 18 cases, 10 cases were within and 2 out of margin according to the Oxford Centre criteria. Radiolucency below the tibial component was seen in 2 cases. Conclusions: This independent study has conþrmed preliminary þndings that using a minimally invasive approach good radiological and clinical results can be obtained. Presence of PFA had no inßuence on good clinical outcome.

Intramedullary (IM) femoral alignment guide for unicondylar knee arthroplasty (UKA) is a classic and generally accepted technique to treat unicompartmental knee osteoarthritis. However, IM system has a risk of excessive blood loss, fat embolism and activation of coagulation.Moreover, the implant placement and limb alignment may be less accurate in IM for UKA than total knee arthroplasty. So we try to use extramedullary (EM) femoral alignment for UKA to avoid above disadvantages. To our knowledge, few current studies have been reported by now. We reported a series of cases treated through a newly developed EM technique and evaluated the accuracy of femoral component alignment and preliminary clinical results. Between January 2009 and January 2010, 11 consecutive patients(15 knees)consisting of 8 males and 3 females were enrolled. There were 7 cases in unilateral knee and 4 cases in bilateral knees. The mean age was 65.2 years (range 60∼72 years). Incision, surgical time, blood loss and complications were measured. The pre- and post operative function of the knees were evaluated by HSS score system. The pre- and postoperative femoral component alignment was measured and compared. All cases were followed up for average 15 months (10-22 months). The mean length of incision was 7.2cm (range 6 to 8cm), the mean surgical time was 115.0min(range 90 to 125min),the mean blood loss was 50.8ml (range 50 to 80ml). The mean preoperative HSS score increased from 75 (range 63 to 83) to 95 (range 88 to 97) postoperatively (p<0.05). All femoral components were within the recommended range for varus/valgus (±10 degree) and lexion/extension (±5 degree) angle. None had complications associated with reamed canal injury. By using our EM technique, we could achieve an accurate femoral component alignment and satisfactory clinical effect. However, strict comparison between EM and cconventional IM technique and large amount of cases are essential. Further mid- and long-term studies are required.

Purpose

To identify the incidence and reasons for revision of the Oxford prosthesis (OXF) in New Zealand.

The purpose of this study was to identify causes of failure and rates of revision of the Oxford prosthesis (OXF) in New Zealand, by reviewing and comparing the uni-compartmental (UKA) and total knee arthroplasty (TKA) data from January 2000 to December 2005, as recorded in the New Zealand National Joint Registry.

Eighty one orthopaedic surgeons performed 2006 Oxford UKAs (64% of all UKAs). The revision rate was 4.7%. This compared with a revision rate of 4.8% for all UKAs combined, and 1.6% for TKA. UKA (3122) made up 13% of all knee arthroplasties (24 260). The most common reasons for revision of the OXF were aseptic loosening (45%), unexplained pain (33%) and bearing dislocation (12%). Unexplained pain as the only reason for revision (33%) was significantly different (p = 0.001) from the TKA rate (23%).

Deep infection as a cause for revision was 0.20% for the OXF compared with 0.48% for TKA (p=0.07). The patient- generated Oxford scores at six months after operation were rated excellent or very good (Field et al, 2004) in 68% of OXF compared with 62% TKA patients (p = 0.001).

Five higher-use OXF surgeons (12 or more/year) performed 25.1% of the operations with a revision rate of 0.99%. Ten high- use surgeons (eight to 11/year) performed 28.1 % of operations with a revision rate 4.6%. Thirty medium-use surgeons (two to seven/year) performed 39.0% of the operations with a revision rate of 6.4%. Thirty-six low-use surgeons (one or less/ year) performed 7.8% of the operations with a revision rate of 8.3%. The difference in revision rate between the higher-use surgeons (one operation/month) and all the other three lower use groups was significant (e.g. p=0.0006 higher/low)

The early revision rate for the OXF was 2.9 times greater than that for TKA. However, higher-use surgeons (i.e. those performing one/month or more) had a revision rate comparable to TKA. Deep infection was lower and six month function scores were higher for OXF compared with TKA. Unexplained pain as the only reason for revision was significantly higher for OXF compared with TKA.

Background. In the United Kingdom (UK), the fastest growing population demographic is the over 85 years of age, but despite this, outcomes achieved in the octogenarian population with a Unicompartmental Knee Replacement (UKR) are underrepresented in the literature. The Elective Orthopaedic Centre, Epsom, has an established patient reported outcome measures (PROMs) programme into which all patients are routinely enrolled. We aim to investigate the outcome of medial UKR using the oxford phase 3 implant in octogenarians. Methods. We retrospectively reviewed our database for patients aged 60–89 years, who underwent a medial unicompartmental Knee Replacement (UKR) using the oxford phase 3 implant, between June 2007-December 2012 (N=395). The patients were stratified into 3 groups based on age, 60–69 (N=188), 70–79(N=149), and 80–89(N=58). Oxford Knee Scores (OKS), Euro-quol (EQ-5D) scores, revision rates, and mortality were compared. Results. We found that the octogenarian group achieved considerable improvement at 1 year with a mean OKS of 39.2 (+/−7.193) and EQ-5D score of 0.791(+/−0.241). And this improvement remained significant at 2 years. There was no difference in functional outcome when the 3 groups were compared. Revision rates for the 3 groups from youngest to oldest were, 8.5%, 4.5%, and 6.9% respectively. Odds ratio and survival analysis showed no significant difference between the groups. Conclusion. In conclusion, we found that octogenarians over a 2 year period achieved similar functional outcome as their younger counterparts. Level of Evidence. IV

Excessive under correction of varus deformity may lead to early failure and overcorrection may cause progressive degeneration of the lateral compartment following medial unicompartmental knee arthroplasty (UKA). However, what influences the postoperative limb alignment in UKA is still not clear. This study aimed to evaluate postoperative limb alignment in minimally-invasive Oxford medial UKAs and the influence of factors such as preoperative limb alignment, insert thickness, age, BMI, gender and surgeon's experience on postoperative limb alignment. Clinical and radiographic data of 122 consecutive minimally-invasive Oxford phase 3 medial unicompartmental knee arthroplasties (UKAs) performed in 109 patients by a single surgeon was analysed. Ninety-four limbs had a preoperative hip-knee-ankle (HKA) angle between 170°-180° and 28 limbs (23%) had a preoperative hip-knee-ankle (HKA) angle <170°. The mean preoperative HKA angle of 172.6±3.1° changed to 177.1±2.8° postoperatively. For a surgical goal of achieving 3° varus limb alignment (HKA angle=177°) postoperatively, 25% of limbs had an HKA angle >3° of 177° and 11% of limbs were left overcorrected (>180°). Preoperative HKA angle had a strong correlation (r=0.53) with postoperative HKA angle whereas insert thickness, age, BMI, gender and surgeon's experience had no influence on the postoperative limb alignment. Minimally invasive Oxford phase 3 UKA can restore the limb alignment within acceptable limits in majority of cases. Preoperative limb alignment may be the only factor which influences postoperative alignment in minimally-invasive Oxford medial UKAs. Although the degree of correction achieved postoperatively from the preoperative deformity was greater in limbs with more severe preoperative varus deformity, these knees tend to remain in more varus or under corrected postoperatively. Overcorrection was more in knees with lesser preoperative deformity. Hence enough bone may need to be resected from the tibia in knees with lesser preoperative deformity to avoid overcorrection whereas limbs with large preoperative varus deformities may remain under corrected

Introduction. Unicompartmental knee arthroplasty (UKA) is a successful procedure for medial compartment osteoarthritis (OA). Recent studies using the same implant report a revision rate of 2.9%. Other centers have reported revision rates as high as 10.3%. The purpose of this study was to retrospectively review the clinical results of Oxford Phase 3 UKA's performed in the setting of isolated medial compartment OA and to compare our results to the previous mid-term studies. Our secondary goal was to determine reasons for revision and evaluate selected independent predictors of failure. Methods. A retrospective review of 465 Oxford Phase 3 medial UKA's performed on 386 patients (222 female; 164 male) with isolated medial compartment OA. The average age at surgery was 69.5 years (40–88). Outcome measures included: Knee Society Scores(KSS), Oxford Knee Scores(OKS), SF-12, WOMAC, revision rates, and patient satisfaction. We evaluated independently predictors of failure including: gender, body mass index(BMI), number of previous surgeries, implant sizes, cement technique (simultaneous vs staged), cement type. Revision rates based upon the polyethylene thickness (defined as thin 3–4 mm; medium 5–6 mm; thick 7–9 mm). The need for stems and augments and the degree of constraint required at revision to a total knee arthroplasty (TKA) were evaluated. Results. At a mean follow-up of 60.7 months (11–114) OKS improved from 21 to 37 points (p<.05). Latest SF-12 score was 43.8 points (16.8–64.7 points; SD, 10.5) and WOMAC was 80 points (23–100 points; SD, 18). The overall revision rate was 6.9% (32/465 knees). Mean time to revision in 25 knees was 34.5 months (7–96), and revision was most commonly performed for lateral compartment OA (10). Eight knees were revised for tibial loosening, femoral loosening (6), and PCL failure (1). Revision implants included posterior stabilized in 13 knees (52%), cruciate retaining in 9 knees (36%), and cruciate substituting/dished in 3 knees (12%). Five revisions (20%) required tibial augments and 2(8%) had cemented tibial stems. The mean revision polyethylene thickness was 12 mm (range, 9–19 mm) and one knee required a constrained polyethylene. Three knees are pending revision to TKA. Four knees underwent poly exchange for bearing dislocation and 3 knees had further arthroscopic procedures. Eighty-four percent of the patella were resurfaced at revision. Three quarters (76%) of the patients were extremely or very satisfied with their surgery. Over 90% would have had their surgeries again. Gender, BMI, number of previous surgeries, femoral or tibial sizing, poly thickness, cementing technique or type did not predict revision, the need for constraint, or the need for stems or augments. Conclusion. Our revision rate of 6.9% was comparable to other midterm studies from independent centers but not as low as recently reported results from Oxford. Progression to lateral compartment OA was the most common reason for revision. We could not find any independent predictors of failures in this group of 465 knees

Aims. Spontaneous osteonecrosis of the knee (SONK) mainly affects the medial femoral condyle, would be a good indication for UKA. The primary aim of this study was to assess the clinical, functional and radiographic outcomes at middle to long-term follow-up, of a consecutive series of fifty UKA used for the treatment of SONK. The secondary aim was to assess the volume of necrotic bone and determine if this influenced the outcome. Patients and Methods. We reviewed 50 knees who were treated for SONK. Patients included ten males and 38 females. The mean age was 73 years (range, 57 to 83 years). The mean height and body weight were, respectively 153 cm (141 ∼171 cm) and 57 kg (35 ∼75kg). All had been operated on using the Oxford mobile-bearing UKA (Zimmer-Biomet, Swindon, United Kingdom) with cement fixation. The mean follow-up period was 8.4 years (range, 4 to 15years). We measured the size (width, length and depth) and the volume to be estimated (width x length x depth) of the necrotic bone mass using MRI in T1-weighted images. The clinical results were evaluated using the Knee Society Scoring System (KSS) and Oxford Knee Score (OKS). The flexion angle of the knee was evaluated using lateral X-ray images in maximum flexion. Results. There were no implant failures, but there were 4 deaths (from causes unrelated to UKA) mean 6.6 years after surgery(5∼8), 3 cases were lost mean 3.3 years after surgery(2∼5). The mean size of the necrotic lesion were 17.2mm (14.7∼25.3) in width, 28.2mm (6.2∼38.3) in length and 11.3mm (3.2∼14.3) in depth. The mean volume of it was calculated to be approximate 5.4 cm. 3. (0.7∼11.1). The mean flexion of the knee, KSS Knee Score, Function Score and OKS increased from a preoperative 128.7 degrees (110 ∼ 140 degrees) to 137.5 degrees (110 ∼ 153 degrees), 52.3 (30 ∼ 64) to 91.3 (87 ∼ 100), 39.7 (15∼ 55) to 90.2 (65 ∼ 100) and 21.6 (12∼ 28) to 40.2 (34∼ 48), respectively at the latest follow-up. At last follow-up all patients had good or excellent OKS. Conclusions. There was a 100% survival rate of the Oxford Phase 3 UKA for SONK in the middle to long-term (up to 15 years after surgery) in this independent study. All patients had good/excellent results at last follow-up and there were no reoperations or major complications. This suggests that Oxford mobile-bearing UKA is a good and definitive treatment for medial femoral SONK, whatever the size of the lesion

Aims

The aim of this study was to determine whether obesity had a detrimental effect on the long-term performance and survival of medial unicompartmental knee arthroplasties (UKAs).

Introduction. Patient Specific Instrumentation (PSI) has the potential to allow surgeons to perform procedures more accurately, at lower cost and faster than conventional instrumentation. However, studies using PSI have failed to convincingly demonstrate any of these benefits clinically. The influence of guide design on the accuracy of placement of PSI has received no attention within the literature. Our experience has suggested that surgeons gain greater benefit from PSI when undertaking procedures they are less familiar with. Lateral unicompartmental knee replacement (UKR) is relatively infrequently performed and may be an example of an operation for which PSI would be of benefit. We aimed to investigate the impact on accuracy of PSI with respect to the area of contact, the nature of the contact (smooth or studded guide surfaces) and the effect of increasing the number of contact points in different planes. Method. A standard anatomy tibial Sawbone was selected for use in the study and a computed tomography scan obtained to facilitate the production of PSI. Nylon PSI guides were printed on the basis of a lateral UKR plan devised by an orthopaedic surgeon. A control PSI guide with similar dimensions to the cutting block of the Oxford Phase 3 UKR tibial guide was produced, contoured to the anterior tibial surface with multiple studs on the tibial contact surface. Variants of this guide were designed to assess the impact of design features on accuracy. These were: a studded guide with a 40% reduction in tibial contact area, a non-studded version of the control guide, the control guide with a shim to provide articular contact, a guide with an extension to allow distal referencing at the ankle and a guide with a distal extension and an articular shim. All guides were designed with an appendage that facilitated direct attachment to a navigation machine (figure 1). 36 volunteers were asked to place each guide on the tibia with reference to a 3D model of the operative plan. The order of placement was varied using a counterbalanced latin square design to limit the impact of the learning effect. The navigation machine recorded deviations from the plan in respect of proximal-distal and medial-lateral translations as well as rotation around all three axes. Statistical analysis was performed on the compound translational and rotational errors for each guide using ANOVA with Bonferroni correction with statistical significance at p<0.05. Results. Contact points in greater than one plane led to a trend for increasing accuracy and precision of PSI guide placement with respect to rotational alignment, this achieved statistical significance relative to the control guide only with the guide that included articular and distal contact points (figure 2). No significant differences were found with respect to translation. Changes in contact area within the same plane and the use of smooth or studded contact points made no significant difference to accuracy. Conclusion. PSI guide design significantly impacts on accuracy of placement. PSI guides for UKR should endeavour to include widely separated reference points in different planes to maximise rotational accuracy

Background. In this study, we investigated the long-term clinical results and survivorship of minimally invasive unicompartmental knee arthroplasty (UKA) by collecting cases that have been implanted for >10 years ago. Methods. Medial UKA on 180 cases in 142 patients was performed over a period of 1 year after the first introduction of minimally invasive UKA from January 2002 to December 2002. Among these, 166 cases in 128 patients who underwent Oxford phase 3 medial UKA using the minimally invasive surgery, with the exclusion of 14 cases including 10 cases of follow-up loss and 4 cases of death, were selected as the subject. The mean age of the patients at the time of surgery was 61 years, and the duration of the follow-up was minimum 10 years. All the preoperative diagnosis was osteoarthritis of the knee joint. Clinical and radiographic assessments were measured by the Knee Society clinical rating system, and the survival analysis was confirmed by the Kaplan–Meier method with 95% confidence interval (CI). Results. The mean Knee Society knee and function scores improved significantly from 53.8 points (25 to 70) and 56.1 points (35 to 80) preoperatively to 85.4 points (58 to100) and 80.5 points (50 to 100) at 10-year follow-up, respectively(P<0.001). The mean range of the motion of the knee joint recovered from 128.6° (110° to 135°) to 132.5o (105o to 135o) (P<0.001), and the tibiofemoral angle changed from the mean 0.2° of varus (7o of varus to 7o of valgus) to 4.6° of valgus (2° of varus to 11° of valgus) under the weight-bearing X-ray (P<0.001). Failures following the UKA occurred in 16 cases in 14 patients out of a total of 166 cases (9.6%), and the mean time of the occurrence of the failure was 6.2 years after the surgery. The causes of the failure included 7 cases of simple dislocation of mobile bearing, 4 cases of loosening of implant, 1 case of dislocation of mobile bearing accompanied by loosening of implant, and 1 case of dislocation of mobile bearing accompanied by the rupture of the medial collateral ligament (MCL). Moreover, there was 1 case of fracture of polyethylene bearing, 1 case of deep infection and 1 case of failure because of medial tibial condylar fracture. Of the total of 16 cases of failures, 11 cases (69%) were treated with revision total knee arthroplasty (TKA), whereas 5 cases (31%) were treated with a simple change of mobile bearing. The 10-year survival rate was 90.5% (95% CI, 85.9 to 95.0) when failure was defined as all the reoperations, whereas the 10-year survival rate was 93.4% (95% CI, 89.6 to 97.1) when the cases in which only revision TKA was defined as failure. Conclusions. The results of this study show outstanding functions of the knee joint and satisfactory 10-year survival rate after minimally invasive UKA. Therefore, minimally invasive UKA could be a useful method in the treatment of osteoarthritis in one compartment of knee joint

Aim: To assess the intra- and inter-observer reliability of using pre-operative templates in selecting the appropriate prosthetic size of the unicompartmental knee system (Oxford Phase3, Biomet Merck, Bridgend) Methods: Ten observers estimated the size of the unicondylar knee prosthesis required for thirty randomly selected patients with osteoarthritis. Estimation of the size was gauged using templates pre-operatively. AP and lateral radiographs were taken of each patient. All observers were orthopaedic surgeons with a minimum of þve years experience in orthopaedic surgery and with a general interest in joint arthroplasty. The observations were recorded independently and repeated measurements were taken two weeks later. Results: Intra- and inter-observer discrepancies were evaluated using the weighted kappa (κ) coefþcient with signiþcant intra- and inter-observer variations. The results are shown in the table. Conclusions: Pre-operative radiological templating is of questionable beneþt in patients undergoing Oxford Phase 3 knee arthroplasty