Hydroxyapatite granules interposed at bone-cement interface in total hip replacements: histological study of retrieved specimens

The effect of hydroxyapatite (HA) granules interposed between bone and polymethylmethacrylate (PMMA) bone cement in total hip replacement was histologically evaluated. The technique consisted of smearing 2-5 g of HA granules (straight phi = 100-300 microm) onto the bone surface just before cementing. Four specimens containing well-fixed bone-cement interface were retrieved at 1, 2, 6, and 10 years postoperatively and examined with back-scattered electron microscopy and light microscopy. The majority of HA granules were incorporated into remodeled trabeculae, and highly convoluted bone-cement interface was maintained up to 10 years. The presence of active remodeling in the adjacent bone was observed. There were no significant inflammatory or foreign body reactions against interposed HA granules. In one specimen retrieved from a patient with rheumatoid arthritis, bone formation around HA granules was limited after 1 year. These results have provided histological evidence for the significantly reduced incidence of radiolucent lines in total hip replacement with this cementing technique, reported elsewhere.     

The survivorship and results of total knee replacements converted from unicompartmental knee replacements

Unicompartmental knee replacements (UKR) converted to total knee replacements (TKR) have often been viewed with scepticism because of the perceived difficulty of revising a UKR to a TKR. We present the survivorship analysis of a 77 patient cohort as well as the current results of a 35 patient cohort. There were a total of 77 patients in the survivorship study with an average follow-up of 6.9 years and an average Bristol Knee Score of 78.5. Using Kaplan-Meier survivorship analysis, a 91% survivorship at 10 years was demonstrated. The average age at revision to TKR was 66.1 years. The average follow-up period was 10.5 years and a recent clinical and radiological review of the 35 living patients showed an average Bristol Knee Score of 78.2 with 16 excellent, 11 good, five fair and three failed. CONCLUSION: The results of the UKRs have already shown it to be safe, reliable and repeatable. We believe that this study shows that revision of UKR to TKR is not technically difficult and that the results are comparable to the results of primary TKRs.     

牛津单髁置换术应用于单间室部分软骨损伤的疗效研究

目的 评估膝关节单髁置换术治疗部分软骨磨损单间室骨性关节炎的疗效。方法 回顾性分析2008年4月至2019年4月在同济大学附属杨浦医院采用膝关节单髁置换术治疗的102例（115膝）内侧间室软骨部分磨损（PTCL）膝骨性关节炎的患者资料,经匹配年龄、性别、体重指数和随访时间的102例（115膝）软骨全层磨损（FTCL）的患者为对照组。采用OKS评分、AKS评分和疼痛视觉模拟评分（VAS评分）对术前、术后膝关节功能进行评估,X线进行影像学评估。结果 所有患者均获得了完整的随访,术后平均随访（60.0±19.6）个月（24～152个月）。FTCL组和PTCL组患者术后末次随访OKS评分、AKS-Knee评分、AKS-Function评分、VAS评分均较术前明显改善（P<0.05）。术后1年、2年和末次随访,PTCL与FTCL组间OKS评分、AKS-Knee评分、AKS-Function评分、VAS评分比较,差异无统计学意义（P>0.05）。共有6膝翻修,FTCL组3膝（2.6%）,PTCL组3膝（2.6%）。结论 不能简单地将PTCL视为膝关节单髁手术禁忌证,应该根据软骨损伤的程...     

单髁关节置换治疗膝内侧骨性关节炎的中短期临床分析

目的评估应用Oxford phase3单髁假体系统进行单髁关节置换治疗膝关节内侧骨性关节炎的中短期临床疗效分析。方法 2007年4月~2014年12月,采用Oxford phase3单髁假体系统,应用微创小切口技术,进行单髁关节置换治疗膝关节内侧骨性关节炎251例(293膝),平均年龄61岁(44~82岁)。以门诊或电话随访,平均随访时间34个月(6~92),随访期间无死亡病例,16例失访。采用KSS评分系统进行术前和术后评分,收集数据,进行统计学分析。术后影像学评估采用牛津标准。结果 KSS评分:膝关节平均评分,术前61(47~82),术后95(88~100);功能平均评分,术前56.2(42~80),术后91.1(72~100),0.05。1例术后迟发性感染;2例术后活动平台聚乙烯衬垫脱位;2例股骨髁假体松动;2例术后出现绞索和弹响影响日常活动,1例术中前交叉韧带止点部分撕脱;3例术后关节活动度少于90°;7例术后出现持续疼痛。以上并发症均出现于术后1年之内。术后影像学评估无外侧间室进行性退变病例。随访终期假体在位率97.2%。结论单髁关节置换治疗膝关节内侧骨性关节炎可以获得良好的中短期临床效果。     

Management of aseptic failure of the mobile-bearing Oxford unicompartmental knee arthroplasty

BackgroundUnicompartmental knee arthroplasty (UKA) accounts for 9.1% of primary knee arthroplasties (KAs) in the UK. However, wider uptake is limited by higher revision rates compared with total knee arthroplasties (TKA) and concerns over subsequent poor function. The aim of this study was to understand the revision strategies and clinical outcomes for aseptic, failed UKAs at a high-volume centre.MethodsThis was a retrospective, single-centre cohort study of 48 patients (31 female, 17 male) with 52 revision UKAs from 2006 to 2018. Median time to revision was 67 (range 4–180) months. Indications for revision were progression of osteoarthritis (n = 31 knees, 59.6%), unexplained pain (n = 10 knees, 19.2%), aseptic loosening (n = 6 knees, 11.5%), medial collateral ligament incompetence (n = 3 knees, 5.8%) and recurrent bearing dislocation (n = 2 knees, 3.8%). Technical details of surgery, complications and functional outcome were recorded.ResultsFailed UKAs were revised to primary TKAs (n = 29 knees, 55.8%), revision TKAs (n = 9 knees, 17.3%), bicompartmental KAs (n = 11 knees, 21.2%), or unicompartmental-to-unicompartmental KAs (n = 3 knees, 5.8%). Median follow up was 81 (range 24–164) months. Four patients (7.7%) died from unrelated causes. No re-revisions were identified. Surgical complications required re-operation in five knees (9.6%). Median Oxford Knee Score at latest follow up was 38 (range 9–48) points and median EQ5D3L index 0.707 (range −0.247 to 1.000).ConclusionsAseptic, revision UKA at a high-volume centre had good clinical outcomes. Bicompartmental KA demonstrated excellent function and should be considered an alternative to TKA for progression of osteoarthritis for appropriately trained surgeons.     

Sporting and physical activity following Oxford medial unicompartmental knee arthroplasty

The purpose of this study was to evaluate and assess the sporting and physical activities of patients who had undergone an Oxford medial unicompartmental knee arthroplasty (UKA). Seventy-six patients who underwent a UKA between 2000 and 2003 were reviewed. Demographic data such as age, sex and comorbidities were recorded. University of California Los Angeles (UCLA) activity level ratings and Oxford knee scores were determined for each patient. The sporting and physical activities of all patients' pre- and post-operatively were recorded. The mean age of patients was 64 years (range 49-81) at surgery and 66 years (range 53-82) at review. The mean follow up time was 18 months (range 4-46). Following surgery there was a significant improvement in UCLA activity level scores from 4.2 to 6.5 (Wilcoxon Matched-pairs Signed-rank Test, p<0.01). Forty-two patients (64%) regularly participated in sport before they became symptomatic with significant knee pain, and thirty-nine patients (59%) regularly participated in sports after surgery. In total 93% of patients successfully returned to their regular sporting and physical activities following surgery. The published long-term survivorship of the Oxford UKA has given surgeons increasing confidence to use the prosthesis on a younger generation of patients. Our study has demonstrated that this population of patients is extremely active. A more detailed study is required to evaluate the long-term effects of sporting activity on the Oxford UKA.     

Comparison of five-year clinical outcomes of 524 cemented and cementless medial unicompartmental knee replacements

AimTo compare the outcomes of cemented and cementless Unicompartmental Knee Replacements (UKR) at 5 years after surgery.Methods262 cemented and 262 cementless medial mobile-bearing UKR, implanted by four high-volume surgeons using identical indications and surgical techniques, were reviewed by independent physiotherapists at 5 years. Survival, Oxford Knee Score (OKS), American Knee Society Score (AKSS), and EQ-5D-5L were assessed. The cementless cohort was mainly implanted after the cemented. Each cohort was divided into early and late sub-groups and compared, to assess if any differences were due to progressive improvement in surgical practice over time.ResultsThere were no significant differences between the cohorts for demographics, pre-operative scores, and 5-year revision (0.8%), re-operation (1.5%), and complication rates (5%). The cementless cohort had significantly better 5-year OKS (43v41, p = 0.008), AKSS-Objective (94v90, p = 0.049) and EQ-5D-5L (0.81v0.87, p = 0.0001). Pain sub-scores within OKS, AKSS, and EQ-5D-5L were also significantly better in the cementless cohort, and the differences were proportionally much greater and more significant than differences in their respective overall scores. There was no significant improvement in scores between the early and late subgroups of the cohorts, whereas the ‘early-cementless’ cohort had significantly better scores than the contemporaneously implanted ‘late-cemented’ cohort. This suggests that differences found were due to implant type, instead of improved surgical practice over time.ConclusionCementless UKR is associated with better clinical outcomes than cemented UKR, which is primarily due to improved pain relief. Both cemented and cementless UKR are safe with low reoperation and complication rates, and a 5-year survival of 99%.     

Sagittal shapes of current fixed-bearing unicompartmental knee replacements differ from those of normal knees

BackgroundThe principle when performing unicompartmental knee replacements (UKR), is to restore the natural alignment as well as the ligament tension. The tension in the ligaments is determined by the position of the joint line and the geometry of the articulating surfaces of the joint. If the surface geometry of the femoral component in a UKR is different from that of the natural knee it might cause abnormal ligament tension. This study was undertaken to determine the surface geometry of the native knee and to compare that with the geometry of different commercially available UKR femoral components.MethodsThirty-six native femurs and seven different UKR femoral component designs were included in this study. The sagittal shapes of the native femoral condyles and the prostheses were quantitatively described with the radius ratio (RR) and transition position index (TPI), which were calculated from the radii and transition point of the extension and flexion facets.ResultsThe different prostheses showed a wider shape variability than the native medial condyles, having at least two times greater coefficient of variation for the RR and TPI. The sagittal shape of three prostheses corresponded to the native medial femoral condyles whereas five prostheses corresponded to the lateral condyles. One prosthesis had curves that fell far outside the native knee shape.ConclusionThere was a wider sagittal shape difference between the femoral components compared to the native knees. Clinically, the sagittal position of the prostheses can compensate for these differences, but it might be technically challenging.     

Radiographic evaluation of factors affecting bearing dislocation in the domed lateral Oxford unicompartmental knee replacement

BackgroundThe rate of bearing dislocation with the domed lateral Oxford Unicompartmental Knee Replacement (OUKR) in different series varies from 1% to 6% suggesting that dislocation is influenced by surgical technique. The aim of this study was to identify surgical factors associated with dislocation.MethodsAligned post-operative antero-posterior knee radiographs of seven knees that had dislocated and 87 control knees were compared. Component alignment and position and the alignment of the knee were assessed. All bearing dislocations occurred medially over the tibial wall.ResultsKnees that dislocated tended to be overcorrected: Compared with those that did not dislocate, they were in 2° less valgus (p = 0.019) and the tibial components were positioned 2 mm more proximal (p < 0.01). Although the relative position of the centre of the femoral component and the tibial component was the same (p = 0.8), in the dislocating group the gap between the edge of the femoral component and the top of the wall in flexion was 3 mm greater (p = 0.019) suggesting that the components were internally rotated.ConclusionsTo minimise the risk of dislocation it is recommended that the knee should not be overstuffed. This is best achieved by selecting the bearing thickness that just tightens the ligaments in full extension, and re-cutting the tibia if necessary. In addition to minimise the gap between the femoral and tibial components through which the bearing dislocates, the femoral component should be implanted in neutral rotation and should not be internally rotated.Level of evidenceLevel IV     

Combined anterior cruciate reconstruction and Oxford unicompartmental knee arthroplasty: in vivo kinematics

The in vivo kinematics of 10 patients after combined anterior cruciate ligament reconstruction (ACLR group) and Oxford unicompartmental knee arthroplasty (UKA) was compared to those of 10 Oxford UKA patients with an intact ACL (ACLI group) and a group of 22 normal knees. The kinematics during a step-up exercise and a deep knee bend exercise was measured using a fluoroscopic technique. The patellar tendon angle (PTA) to knee flexion angle relationship during both exercises was similar for all three groups of subjects. For the UKA groups the pattern of mobile bearing movement during both exercises was similar. This study demonstrates that normal knee kinematics is achieved in the ACL deficient arthritic knee following ACLR and UKA. As a result these patients, who tend to be young and high demand, have excellent outcome and achieve high levels of function. As the relative position of the components and thus component loading are similar to the ACLI UKA, we would expect similar long term survival.     

Revision of Oxford medial unicompartmental knee arthroplasty to total knee arthroplasty - results of a multicentre study

The advantages of Unicompartmental Knee Replacement (UKR) over Total Knee Replacement (TKR) includes the preservation of soft tissue as well as bone stock, and better function with improved range of motion and more natural gait. It is therefore believed that the revision of failed UKR to TKR is technically easier than revision of failed TKR. In our study we tested this hypothesis by assessing the reconstruction requirements and early clinical and radiological outcome following the revision of UKR to TKR. During a 15-year period 1060 primary Oxford medial UKR procedures were performed at three centres, 36 of which underwent revision to TKR due to aseptic failure. The mean operating time for revision surgery was 113 min. Among the revision prostheses used, 28 were standard TKRs, six were constrained, and two were semi-constrained. Thirty had no intramedullary stems whereas six had intramedullary stems. In 30 cases reconstruction for bone loss was not required whereas metal augmentation was used in two knees, contained peg defects in the femur were filled with cement in two knees and contained keel defects in the tibia were grafted using the bone from revision cuts in two knees. After a mean follow-up of 2 years, the mean 'total knee score' was 86.3 and the mean functional score was 78.5. These findings suggest that the complexity of operation and complications encountered during Oxford medial UKR revision and the clinical outcome compare favorably with those of TKR revision.     

第三代牛津单髁系统在膝关节内侧间室骨性关节炎的应用

目的探讨牛津第三代单髁假体微创单髁置换术治疗膝关节内侧间室骨性关节炎的疗效与技术。方法回顾性分析2005年5月~2011年6月采用微创单髁置换术治疗100例膝关节内侧间室骨性关节炎患者的资料,对患者术前、术后膝关节疼痛及关节活动度进行评估(HSS评分法),并测量术后假体力线,分析假体设计、手术适应证的选择及手术技术。结果 100例术后平均随访36个月(12~75个月),末次随访时膝关节HSS评分和膝关节活动度明显增加,股骨假体力线平均为0.69°内旋±3.18°,0.83°伸直±3.63°,胫骨假体力线平均为0.12°内翻±0.80°,0.39°伸直±1.24°,无假体位置不良、脱位及假体松动等并发症。结论微创单髁置换术治疗膝关节内侧间室骨性关节炎具有很好的疗效,其关键在于手术适应证的选择和手术技术。     

Stress shielding in bone of a bone-cement interface

Cementation is one of the main fixation methods used in joint replacement surgeries such as Total Knee Replacement (TKR). This work was prompted by a recent retrieval study [1], [2], which shows losses up to 75% of the bone stock at the bone-cement interface ten years post TKR. It aims to examine the effects of cementation on the stress shielding of the interfacing bone, when the influence of an implant is removed.A micromechanics finite element study of a generic bone-cement interface is presented here, where bone elements in the partially and the fully interdigitated regions were evaluated under selected load cases. The results revealed significant stress shielding effect in the bone of all bone-cement interface regions, particularly in fully interdigitated region. This finding may be useful in the studies of implant fixation and other related orthopedic treatment strategies.     

Meniscal bearing dislocation while rolling over in sleep following Oxford medial unicompartmental knee arthroplasty

Meniscal bearing dislocation while rolling over in sleep has never been reported in Oxford unicompartmental knee arthroplasty (UKA). This study reports two cases of meniscal bearing dislocation into the intercondylar ridge while rolling over in sleep. In the case of one patient, closed reduction of the bearing was performed, and the use of a knee brace was effective in preventing re-dislocation. In the second patient, closed reduction was possible; however, bearing dislocation was repeated. Therefore, revision surgery was performed by replacing the tibial component and using a thicker bearing. The common features in dislocation during rolling over while sleeping in both cases were dislocation into the intercondylar ridge, the combination of small femur and AA-size tibia components, and osteonecrosis. As determined by intraoperative testing, valgus position of the knee while rolling over in sleep could induce bearing dislocation into the intercondylar ridge.

Cementless medial Oxford unicompartmental knee replacement. Five-year results from an independent series

BackgroundUnicompartmental knee replacement (UKR) is a common treatment option for patients with advanced medial compartment knee arthritis. The Oxford UKR (OUKR) is the most commonly used implant for partial knee replacement. A cementless Oxford prosthesis was introduced in 2004 aiming to reduce the revision rate by potentially reducing radiolucencies as well as errors of cementation associated with the cemented prosthesis. Whilst results from the designer centre have been reported, there is little independent clinical evidence of outcomes.The aim of this study was to evaluate the survival of the cementless OUKR in a single surgeon series at an independent centre and to assess clinical and radiographic outcomes.MethodsAll patients who received a cementless medial OUKR and had a minimum of five-year follow-up were included in the series. The Oxford knee score was used to evaluate patient outcomes at five years postoperatively. Survival rates, complications and evidence of radiolucencies on plain radiographs were also reviewed.ResultsOne hundred and fifty-eight cementless medial OUKR were implanted in 126 patients. Three patients died and four knees were revised. The five-year survival was 97.4% and the median Oxford knee score was 43 at five years postoperatively. No Complete radiolucent lines were observed on radiographs at one year. Four tibial components subsided.ConclusionsThis independent series shows that low revision rates and excellent results can be achieved with the use of the cementless OUKR at five years. Early subsidence of the tibial component, which is specific to the cementless prosthesis, warrants further investigation.     

The Oxford medial unicompartmental knee replacement: Survival and the affect of age and gender

Study aimsTo determine the survival and functional outcome for the phase 3 Oxford unicompartmental knee replacement (UKR) performed at a single independent centre and to assess whether age and gender affect survival.Patients and methodsBetween 2000 and 2008, 459 consecutive Oxford UKRs were implanted in 392 patients using a minimally invasive technique.ResultsMean age of patients was 63.0 years and 53% were female. Mean follow-up was 4.4 years (range 0.5–11.2 years). No patient was lost to follow-up and 411 (90%) knees had a minimum follow-up of 2 years. Twenty knees (4.4%) have undergone revision to total knee replacement at a mean time of 3.2 years. Aseptic component loosening (n = 11) accounted for most failures. Cumulative survival was 94.4% at 5 years (95% confidence interval 90.9–97.0) and 93.0% at 8 years (95% confidence interval 84.8–96.2). The median postoperative Oxford knee score was 31.2% (interquartile range 12.2%–52.1%) at latest follow-up. Age and gender had no statistically significant affect on UKR survival.ConclusionsThis large independent series demonstrates good medium-term survival and functional outcome can be achieved with the phase 3 Oxford UKR in appropriately selected patients. Age and gender should not be considered contraindications for performing Oxford UKR.     

Impact of joint line orientation on clinical outcomes in bilateral Oxford mobile-bearing unicompartmental knee arthroplasty

BackgroundJoint line orientation angle (JLOA) is the angle between the knee joint line and the floor. It has been reported to be related to postoperative outcome after TKA. Regarding unicompartmental knee arthroplasty (UKA), although it can be horizontal after UKA because it is a resurfacing surgery, there are few reports about the JLOA after UKA and its impact on clinical outcomes.PurposeThe purpose of this study was to reveal the relationship between JLOA and clinical outcome after UKA.MethodsThis study included 106 knees in 53 consecutive patients with osteoarthritis who underwent simultaneous bilateral mobile-bearing UKA. Their pre- and postoperative JLOAs were measured by full-leg-length standing coronal radiographs. We also evaluated the tibial component height (TCH) as the factor which we assumed could influence JLOA. We analyzed the patients’ JLOAs, TCHs and clinical outcomes.ResultsPre- and postoperative JLOA were 0.4 ± 2.4° and 2.7 ± 2.6°, respectively. The JLOA significantly tilted medially (P < 0.0001). The JLOA significantly negatively correlated with the improvement of the clinical outcomes (Oxford Knee Score (OKS): r = 0.40, P < 0.0001, Knee Society Knee Score (KSKS): r = 0.25, P < 0.01, Knee Society Function Score (KSFS): r = 0.22, P = 0.02). The TCH showed a positive correlation with postoperative JLOA and with the postoperative JLOA change (r = 0.45, P < 0.001; r = 0.25, P < 0.01, respectively).ConclusionThe JLOA significantly tilted medially after UKA. An excessive medial tilt of the JLOA was associated with poorer postoperative outcomes of UKA. It is therefore recommended to keep the JLOA horizontal and to avoid a lower tibial cut.     

Influence of tibial component rotation on short-term clinical outcomes in Oxford mobile-bearing unicompartmental knee arthroplasty

Background

Malposition of tibial components is an important factor for complications in unicompartmental knee arthroplasty (UKA), but the direct relationship between clinical outcomes and position of tibial component remains unknown. We aimed to investigate whether tibial component rotation in the axial plane could affect clinical outcomes after UKA.

Efficacy of an accelerated recovery protocol for Oxford unicompartmental knee arthroplasty--a randomised controlled trial

Unicompartmental knee arthroplasty (UKA) is appropriate for one in four patients with osteoarthritic knees. This study was performed to compare the safety, effectiveness and economic viability of a new accelerated protocol with current standard care in a state healthcare system. A single blind RCT design was used. Eligible patients were screened for NSAID tolerance, social circumstances and geographical location before allocation to an accelerated recovery group (A) or standard care group (S). Primary outcome was the Oxford Knee Assessment at 6 months post operation, compared using independent Mann-Whitney U-tests. A simple difference in costs incurred was calculated. The study power was sufficient to avoid type 2 errors. Forty-one patients were included. The average stay for Group A was 1.5 days. Group S averaged 4.3 days. No significant difference in outcomes was found between groups. The new protocol achieved cost savings of 27% and significantly reduced hospital bed occupancy. In addition, patient satisfaction was assessed as greater with the accelerated discharge than with the routine discharge time. The strict inclusion criteria meant that 75% of eligible patients were excluded. However, a large percentage of these were due to the distances patients lived from the hospital.     

牛津双柱单髁置换术与全膝关节置换术治疗膝内侧骨关节炎的近中期疗效对比

目的:探讨牛津双柱单髁置换术(UKA)与全膝关节置换术(TKA)治疗膝内侧骨关节炎的近中期疗效。方法:回顾性队列研究。纳入2016年10月—2019年11月安徽医科大学第四附属医院50例膝关节内侧间室骨关节炎患者的临床资料。其中,采用牛津双柱UKA治疗的25例(25膝)为UKA组,男7例、女18例,年龄54～81岁;采...