Unicompartmental Knee Replacement Research Articles

ФУНКЦИОНАЛЬНАЯ ОЦЕНКА РЕЗУЛЬТАТОВ ПРОКСИМАЛЬНОЙ СЕГМЕНТАРНОЙ РЕЗЕКЦИИ МАЛОБЕРЦОВОЙ КОСТИ ПРИ ОСТЕОАРТРОЗЕ МЕДИАЛЬНОГО ОТДЕЛА КОЛЕННОГО СУСТАВА

Osteoarthritis (OA) of the knee joint is the commonest form of OA. It occurs commonly in the medial compartment because of a preponderance of varus knees. High tibial osteotomy, total knee replacement and unicompartmental knee replacement are technically demanding procedures, while proximal segmental fibular resection (PSFR) significantly relieves pain and improves joint function in knee osteoarthritis (OA). This study was conducted at the department of traumatology and orthopedics at the Belarusian state medical university. The objective of this study was to assess functional outcomes after PSFR and its correlation with bone mineral density. 23 patients with unicompartmental OA with varus deformity were included in the study. Inclusion criteria included patients with moderate-to-severe symptomatic medial unicom- partmental OA of the knee, who had an indication for a surgical procedure, and who were able to give informed consent for the surgery. Exclusion criteria included patients with posttraumatic knee OA or inflammatory joint disease and patients with a history of previous operations or fractures the primary outcome was measured by calculating the ratio of knee joint space. The secondary outcome measure was pain measured by the visual analog scale (VAS).

Less pain reported 5 years after cementless compared to cemented unicompartmental knee replacement: an analysis of pain, neuropathy, and co-morbidity scores

PurposeTo compare patient-reported pain scores and assess the influence of neuropathy and co-morbidity, on knee pain following cemented and cementless medial unicompartmental knee replacement (UKR) 5 years after surgery.MethodIn this longitudinal study, 262 cemented and 262 cementless Oxford UKR performed for the same indications and with the same techniques were recruited. Patients were reviewed at five years, evaluating patient-reported pain and association with clinical outcomes. Intermittent and Constant Osteoarthritis Pain (ICOAP), PainDETECT (PD), Charnley score, Oxford Knee Score (OKS) and American Knee Society Score (AKSS) were compared.ResultsIn both cohorts, intermittent pain was more common than constant pain (47% vs 21%). Cementless knees reported significantly less pain than cemented (ICOAP-Total 5/100 vs 11/100, p < 0.0001). A greater proportion of cementless knees experienced no pain at all (ICOAP = 0/100, 61% vs 43%, p < 0.0001) and 75% fewer experienced severe or extreme pain. Pain sub-scores in PD, OKS and AKSS follow this trend. Pain was unlikely to be neuropathic (PD positive: 5.26%), but patients reporting high levels of ‘strongest’ pain were three times more likely to be neuropathic. Patients with co-morbidities (Charnley C) experienced greater pain than those without (Charnley A+B) across all knee-specific scores, despite scores being knee specific.ConclusionBoth cemented and cementless UKR in this study had substantially less pain than that reported in literature following TKR. Cementless UKR had significantly less pain than cemented UKR in all scores. Two-thirds of patients with a cementless UKR had no pain at all at 5 years, and pain experienced was most likely to be mild and intermittent with no patients in severe or extreme pain. Patients with cementless UKR that had higher levels of pain were more likely to have co-morbidity or evidence or neuropathic pain. It is unclear why cementless UKR have less pain than cemented; further study is necessary.

Mechanisms of mobile bearing dislocation in lateral unicompartmental knee replacement.

Mobile bearing dislocation occurs in 1- 6% of Oxford Domed Lateral replacements. Dislocations are predominantly medial, but can occur anteriorly or posteriorly. They tend to occur when the knee is flexed. It is not clear how dislocations can be prevented. A previously described mechanical rig for assessing mobile bearing dislocation was updated so as to study dislocation with the knee in flexion. Sub-categories for the description of each type of dislocation were introduced. Dislocation was only possible when the knee was distracted. As the amount of distraction possible in the knee is variable, the risk of dislocation is related to the amount of distraction in the rig necessary for a dislocation. The type of dislocation requiring the least distraction was medial `edge' dislocation in which the edge of the bearing dislocates onto the tibial wall, which is the most common type of dislocation. The amount of distraction necessary decreased the further the bearing was from the wall and with 50% posterior overhang. Rotation of the knee did not influence the amount of distraction. In conclusion dislocation can only occur if the lateral compartment is distracted. To reduce the dislocation risk, surgeons should aim to position the femoral and tibial components so that the bearing is as close as possible to the wall without jamming against it and the tibial component should be positioned flush with the posterior tibial cortex. If, during the surgery, the mobile bearing can easily be dislocated onto the wall the surgeon should consider changing to a fixed bearing. The tibial component should also be positioned flush with the posterior tibial cortex, as if it is too far forward this may contribute to dislocation.

Fixed lateral unicompartmental knee replacement is a reliable treatment for lateral compartment osteoarthritis after mobile-bearing medial unicompartmental replacement

PurposeLateral osteoarthritis following medial unicompartmental knee replacement (UKR) is usually treated with total knee replacement, however, lateral UKR is a less invasive option that preserves a well-functioning medial UKR. This study aimed to determine the 5-year outcome of the cemented Fixed Lateral Oxford UKR (FLO) when used for the treatment of severe lateral disease after medial Oxford unicompartmental knee replacement.MethodsForty-four knees with lateral bone-on-bone osteoarthritis (n = 43) and avascular necrosis (n = 1) treated with the FLO following medial Oxford UKR were followed up prospectively. The Oxford Knee Score (OKS) and Tegner Activity Score (TAS) were collected pre- and post-operatively. Life-table analysis was used to determine survival rates.ResultsThe mean patient age at the time of FLO surgery was 74.4 years with a mean time of 12.1 years between the primary medial UKR and the conversion to a bi-UKR with a FLO. Mean follow-up of the FLO was 3.5 years. After FLO no intra-operative or medical complications, re-admissions, or mortality occurred. There was one reoperation in which a bearing was exchanged for a medial bearing dislocation. There were no revisions of the FLO, so the FLO survival rate at 5 years was 100% (24 at risk). The mean pre-operative OKS was 22, which significantly (p < 0.0001) improved to a mean of 42, 42, and 40 at 1, 2, and 5 years, respectively. The median TAS had a non-significant improvement from 2.5 (Range 0–8) pre-operatively to 2 (Range 1–6) at 5 years postoperatively.ConclusionThe FLO is a reliable treatment for lateral osteoarthritis following medial UKR. At 5 years there was a 100% survival of the FLO with a mean OKS of 40.Level of evidenceIV, Prospective Case Series.

A Comparison of the Periprosthetic Fracture Rate of Unicompartmental and Total Knee Replacements: An Analysis of Data of >100,000 Knee Replacements from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man and Hospital Episode Statistics.

Periprosthetic fractures are rare but devastating complications of knee replacement, often requiring complex surgery with substantial morbidity and mortality. It is not known how the fracture rates after total knee replacement (TKR) and unicompartmental knee replacement (UKR) compare. We performed the first matched study comparing TKR and UKR periprosthetic fracture rates. This study involved 54,215 UKRs and 54,215 TKRs, identified in the National Joint Registry and Hospital Episodes Statistics database, which were propensity score-matched on patient and surgical factors. The International Classification of Diseases, Tenth Revision, (ICD-10) code M96.6 was used to identify periprosthetic fractures at ≤3 and >3 months postoperatively, as well as estimate rates at up to 10 years. Subgroup analyses were performed in different age groups (<55, 55 to 64, 65 to 74, and ≥75 years), body mass index (BMI) categories (normal, 18.5 to <25 kg/m 2 ; overweight, 25 to <30 kg/m 2 ; obese, 30 to <40 kg/m 2 ; and morbidly obese, ≥40 kg/m 2 ), and sexes. The 3-month fracture rate was 0.09% (n = 50) in the UKR group and 0.05% (n = 25) in the TKR group, with this difference being significant (odds ratio [OR], 2.0; p = 0.004). The rate of fractures occurring at >3 months was 0.32% (n = 171) in the UKR group and 0.61% (n = 329) in the TKR group (OR, 0.51; p < 0.001). At 10 years, the cumulative incidence of fractures was 0.6% after UKR versus 1% after TKR (OR, 0.68; p < 0.001). Fracture rates increased with increasing age, decreasing BMI, and female sex for both UKRs and TKRs. The fracture risk was small after both UKR and TKR, with small absolute differences between implant types. During the first 3 postoperative months, the fracture rate after UKR was 0.1% and was about twice as high as that after TKR. However, over the first 10 years, the cumulative fracture rate after TKR was 1% and was almost twice as high as that after UKR. Fracture rates after both UKR and TKR were higher in women, patients ≥75 years of age, and patients with normal weight. Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Current State of Knee Arthroplasty in Russia: Analysis of 36,350 Сases from the Register of the Vreden National Medical Research Center of Traumatology and Orthopedics

Background.Nowadays the knee arthroplasty register of the Vreden National Medical Research Center of Traumatology and Orthopedics (hereinafter referred to as the Vreden Center) contains clinical and statistical data on more than 39,000 primary and revision knee replacements, that mimics current state of this kind of surgery in Russia.&#x0D; Aimofthestudy to analyze the last decade trends in primary knee arthroplasty in largest Russian arthroplasty center.&#x0D; Methods.Data were obtained from the register of the Vreden Center for the period from 2011 to 2022. Information on knee arthroplasty included epidemiologic and numerous peri-operative data including type of surgery and implant, degree of constrain, primary patella resurfacing etc.&#x0D; Resultsanddiscussion.From 2011 to 2022, 36,350 (92.3%) primary arthroplasties performed at the Vreden Center.&#x0D; The number of interventions increased more than twice: from 1,678 in 2011 to 3,924 in 2022. Similar trends observed in Australia and Sweden, where the number of knee arthroplasties increased by 8.2% and 8% in 2021 compared to 2020, respectively. The frequency of primary patellar resurfacing at the Vreden Center was 2.2% over the entire period of observation. On the contrary, the rate of patella replacement increased from 41% in 2005 to 76.1% in 2021 in Australia and from 24.4% in 2015 to 31.9% in 2020 in Switzerland. The partial knee arthroplasty showed enormous growth more than 14 times: from 0.3% in 2011 to 4.3% in 2022 at the Vreden Center. Worldwide unicompartmental knee replacement is still less popular than total and its number widely varies: 4.2% in the USA, 6.9% in Australia, 9.2% in Canada, 11.9% in Norway, 12.8% in Sweden, and 18.4% in Switzerland. Posterior cruciate ligament (PCL) retaining total knee arthroplasties (TKA) prevailed at the Vreden Center: 68.3%, while in other countries it utilize even more widely: 70.5% in Norway, 75% in New Zealand and 93.5% in Sweden.&#x0D; The total length of hospital stay (LOS) decreased dramatically from 19.6 in 2011 to 8.6 in 2022 at the Vreden Center. Nevertheless, there are still opportunities to improve it: by the way in Canada the average LOS for TKA is 2.3 and the USA 0.8 and 1.7 for partial and total arthroplasty, respectively.&#x0D; Conclusion.The main current trends of knee arthroplasty in Russia are the following: increase the number of surgeries, reduced LOS, TKA without patella resurfacing and with PCL retention, finally the growth of partial knee arthroplasties.

Comparison of cementless twin-peg, cemented twin-peg and cemented single-peg femoral component migration after medial unicompartmental knee replacement: a 5-year randomized RSA study

BackgroundThe component design and fixation method of joint arthroplasty may affect component migration and survival. The aim of this study was to compare fixation of cementless twin-peg (CLTP), cemented twin-peg (CTP) and cemented single-peg (CSP) femoral components of medial unicompartmental knee replacement (UKR).MethodsEighty patients (mean age = 63 years, 48 males) with medial knee osteoarthritis were randomized in three ways to CLTP (n = 25), CTP (n = 26) or CSP (n = 29) femoral UKR components. The patients were followed 5 years postoperatively with RSA, bone mineral density (BMD), PROMs and radiological evaluation of radiolucent lines (RLL), femoral component flexion angle and complications.ResultsAt the 5-year follow-up, femoral component total translation was comparable between the three groups (p = 0.60). Femoral component internal rotation was 0.50° (95% CI 0.3; 0.69) for the CLTP group, 0.58° (95% CI 0.38; 0.77) for the CTP group and 0.25° (95% CI 0.07; 0.43) for the CSP group (p = 0.01). BMD decreased peri-prosthetically (range − 11.5%; − 14.0%) until 6-month follow-up and increased toward the 5-year follow-up (range − 3.6%; − 5.8%). BMD change did not correlate with component migration. Lower flexion angle was correlated with higher 5-year subsidence, total translation, varus rotation and maximum total point motion (p = 0.01). Two patients (1 CLTP, 1 CTP) had RLL in the posterior zone. There were two revisions.ConclusionAt 5-year follow-up, fixation of UKA femoral components with twin-peg was not superior to the single-peg design. Cementless and cemented twin-peg femoral components had similar fixation. A lower flexion angle was correlated with higher component migration.

Hinge prostheses in the revision of unicompartmental knee replacement: a descriptive analysis of data from the national joint registry for England, Wales and Northern Ireland.

Unicompartmental knee replacement (UKR) is an effective surgical strategy in patients with isolated medial or lateral compartment osteoarthritis. Study aims were to (1) describe the epidemiology of patients undergoing revision of UKR to a hinge knee replacement (HKR); (2) identify factors influencing time to revision; (3) evaluate HKR survival. An analysis of National Joint Registry data was undertaken, exploring revision of UKR to HKR between 2007 and April 2021. Descriptive analysis of eligible patients and Cox Regression to identify key determinants of time to revision were performed. Failure of HKR post-revision was assessed using survival analysis. 111 patients underwent revision of UKR to HKR. Median age at revision was 70years and most common indications were instability (n = 42) and infection (n = 22). The most common implant was a rotating HKR. Significant independent factors associated with earlier revision were periprosthetic fracture (p = 0.03) and malalignment (p = 0.03). Progressive osteoarthritis (p = 0.01) and higher ASA grades (3: p = 0.01, 4: p < 0.01) delayed time to revision; patient sex and age were not significant factors. Ten patients required subsequent re-revision; median age at re-revision was 61years. HKR revised from UKR had an 89.3% revision-free risk at 5years. Male sex (p < 0.01) and younger age (p < 0.01) were associated with re-revision. Factors associated with time to revision may be used to counsel patients prior to UKR. The survivorship of the HKR of 89.3% at 5years is concerning and careful consideration should be given when using this level of constraint when revising UKR in younger or male patients.

DIFFERENCES IN EARLY RECOVERY FOLLOWING UNICOMPARTMENTAL KNEE ARTHROPLASTY WITH DAY-CASE AND STANDARD CARE PATHWAYS, ASSESSED USING NOVEL PATIENT-REPORTED MEASURES

AbstractBackgroundDaycase pathways which aim to discharge patients the same day following Unicompartmental Knee Replacement have been introduced in some centres, though most continue with Standard pathways. While Daycase pathways have cost savings, recovery data comparing pathways is limited. This study aims to compare patient-reported early recovery between Daycase and Standard pathways following UKR.MethodThis study was carried out in two centres that originally used the same Standard recovery pathway for UKR. In one centre, the Standard pathway was modified into a Daycase pathway. 26 Daycase-Outpatient, 11 Daycase-Inpatient, and 18 Standard patients were recruited. Patients completed the Oxford Arthroplasty Early Recovery Score (OARS) and SF-36 (Acute) measure between Days 1–42.ResultsStandard patients had significantly better Day-1 scores than Daycase patients, but this difference rapidly diminished, and from Day-3 onwards both groups had near-identical scores (OARS Day-1, 59 vs 37, p=0.002, stemming from differences in Pain, Nausea/Feeling-Unwell, Function/Mobility subscores p=0.003,0.014,0.011. OARS Day-3 48 vs 49, p=0.790).Daycase-Outpatients had a higher overall OARS (p=0.002), recovering 1–2 weeks faster than Daycase-Inpatients. OARS subscores demonstrated that Daycase-Outpatients had better Pain, Nausea/Feeling-Unwell, Fatigue/Sleep scores (p=0.020,0.0004,0.019 respectively). SF-36 scores corroborate OARS scores.ConclusionThe Standard cohort had better Day-1 scores than the Daycase cohort, likely due to later mobilisation and stronger inpatient analgesia; these differences diminished by Day-3. Daycase-Outpatients recovered substantially faster than Daycase-Inpatients – likely due to the factors that delayed their discharge. The convergence of scores at 6 weeks demonstrates that both pathways have similar early recovery outcomes.

DOES OBESITY HAVE AN EFFECT ON PATIENT OUTCOMES AND PLATE SURVIVORSHIP IN HIGH TIBIAL OSTEOTOMY SURGERY? THE TOMOFIX ANATOMICAL MEDIAL HIGH TIBIAL PLATE

AbstractIntroductionSurgery in patients with high body mass index (BMI) is more technically challenging and associated with increased complications post-operatively. Inferior clinical and functional mid-term results for high BMI patients undergoing high tibial osteotomy (HTO) relative to normal weight patients have been reported. This study discusses the clinical, radiological and functional outcomes of HTO surgery in patients with a high BMI.MethodThis is a retrospective study on patients undergoing HTO surgery using the Tomofix anatomical MHT plate between 2017 and 2022, with follow-up period of up to 5 years. The cohort was divided: non-obese (BMI &lt;30 kg/m2) and obese (BMI&gt;30 kg/m2). Pre and post operative functional scores were collected: Oxford Knee Score (OKS), EuroQol-5D and Tegner. Complications, plate survivorship and Mikulicz point recorded.Results32 HTO procedures; 19 patients BMI &lt;30 (average 27.0) and 14 patients BMI &gt;30 (average 36.1). In BMI&lt;30 cohort, one readmission for investigation of venous thromboembolism, doppler negative; two complications: hinge fracture and stitch abscess. The five year survivorship of the plate was 100%. In BMI&gt;30 cohort, one readmission for pulmonary embolism; one complication: hinge fracture. The 5 year survivorship of the plate was 93%, 1 conversion to unicompartmental knee replacement. The average OKS improvement was 17 and 18 for BMI &lt;30 and &gt;30 respectively. Mikulicz point change was identical.ConclusionThe Tomofix anatomical MHT plate achieves good outcomes and minimal complications irrespective of BMI. Reduced plate survivorship, thus earlier conversion may be required in the obese, however higher cohort numbers are needed to confirm this.

EARLY TIBIAL SUBSIDENCE OF THE CEMENTLESS OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY

AbstractIntroductionAnecdotal reports suggest some cementless Oxford Unicompartmental Knee Replacements (OUKRs) have painful early subsidence of the tibial component with valgus rotation and/or posterior tilting. The incidence of subsidence and its association with pain is poorly understood. This radiographic study aimed to evaluate the incidence of tibial subsidence and five-year patient reported outcome measures (PROMs) of a cementless OUKR cohort.MethodologyCementless OUKRs from a high-volume centre with acceptable post-operative and five-year radiographs were included. Subsidence was determined by measuring the angle of the tibial tray/tibial axis angle and distance between the tibial tray axis and fibula head on anteroposterior and lateral radiographs using a custom MATLAB program. Analysis of 5-year PROMs assessed the relationship between subsidence and pain. Radiographs indicating tibial subsidence were validated by two observers.ResultsRadiographs of 94 cementless OUKRs were analysed of which five tibial components had subsided (incidence=5%) with an average of 1.92° varus rotation and 2.97° posterior tilt. Subsidence appeared to occur within the first post-operative year with all tibial components fixed securely at 5 years. Two subsiders had moderate pain (ICOAP=20.5,15.9, AKSS Pain=20,45) and lower Oxford Knee Scores (OKS=26,31) compared to the cohort means (ICOAP=3.91, AKSS Pain=45.9, OKS = 43.6). These two subsiders had BMIs greater than 30.ConclusionThis study found 5% of cementless OUKRs in the cohort underwent tibial subsidence. Subsidence with moderate pain occurred in 2% of cases, and pain may be associated with obesity. A larger study is needed to study subsidence in greater detail.

POLYETHYLENE BEARING WEAR OF THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY: TEN-YEAR RESULTS OF A RANDOMIZED CONTROLLED TRIAL COMPARING CEMENTED AND CEMENTLESS FIXATION

AbstractIntroductionThe Oxford Unicompartmental Knee Replacement's (OUKR's) fully-congruent design minimises polyethylene wear. Consequently, wear is a rare failure mechanism. Phase-3 OUKR linear wear at 5 years was higher than previous OUKR phases, but very low compared to fixed-bearing UKRs. This study aimed to measure OUKR bearing wear at 10 years and investigate factors that may affect wear.MethodologyBearing thickness for 39 OUKRs from a randomised study was calculated using radiostereometric analysis at regular intervals up to 10 years. Data for 39 and 29 OUKRs was available at 5 and 10 years, respectively. As creep occurs early, wear rate was calculated using linear regression between 6 months and 10 years. Relationships between wear and patient factors, fixation method, Oxford Knee Score (OKS), bearing position, and component position were analysed.ResultsThe mean wear rate was 0.06mm/year. Fixation method, age, OKS, component size, and bearing size had no correlation with wear. A higher BMI was associated with lower wear (p=0.01). Bearings more than 4mm from the wall had significantly more wear (p=0.04) than those less than 4mm from the wall. There was a linear correlation between the femoral component contact area on the bearing and wear (p=0.04).ConclusionsPhase-3 bearing wear rate is constant, significantly higher than previous OUKR phases at 10 years, and may increase the risk of long-term bearing failure. To minimise complications associated with wear, size 4 bearings should be used in young patients and manufacturing bearings from more durable, highly crosslinked polyethylene should be studied.

The Reliability of the Divergence Angle for Evaluating Rotational Implant Positioning in Medial Unicompartmental Knee Replacement.

Background Unicompartmental knee arthroplasty (UKA) is a highly effective surgical procedure used to treat patients with osteoarthritis affecting a single knee compartment. UKA has gained significant popularity, accompanied by an expansion of its surgical indications. This increasing trend can be attributed to the consistently excellent clinical outcomes associated with UKA, which rival those achieved with total knee arthroplasty (TKA). However, despite these advancements, implant rotation malposition remains a prevalent factor contributing to early failure in UKA cases. The aim of this study is to analyze the rotational positioning of femorotibial implants in UKA and to identify an appropriate angle formed by the femoral component and the tibial component using a newly described angle. Methods This was a retrospective study of patients' data of 40 medial UKA cases of 33 patients who were operated on in our hospital between October 1998 and March 2019. The study introduces a new angle called the "divergence angle." This angle is formed between the lateral portion of the femoral component and the lateral part of the tibial component, as measured on a patellofemoral Merchant view at 30 degrees of knee flexion. The divergence angle was evaluated through radiographic assessment by two independent reviewers. Results According to statistical analysis, the divergence angle was highly reliable with both intra- and inter-observer reproducibility. Intra-observer reproducibility was excellent with an intra-class correlation coefficient(ICC) between 0.901 and 0.933 (p < 0.001). The inter-observer reproducibility was excellent with an ICCof 0.92 (p < 0.001).The Gaussian curve confirmed the normal distribution of the divergence angle values with moderate dispersion of values. The majority of the angles of divergence (85%) measured between the femoral and tibial components were less than 10 degrees (n = 34), with a mean angle of 6.3 ± 4.5°. Conclusion The divergence angle between the femoral and tibial components, measured at 30 degrees of knee flexion using the Merchant view, is an easily accessible, reliable, and reproducible method. This technique enables the assessment of the optimal rotational positioning of implants in medial UKA.

Radiographic retrospective cohort on medial tibial bone loss for fixed bearing unicompartmental knee arthroplasty and total knee arthroplasty at a three-year period

Background: Early post-operative medial tibial bone loss in both unicompartmental knee replacement and total knee replacement has been reported in our previous studies and many other studies. Significant bone loss can contribute to a tibial stress fracture, bone pain and early implant failure. The bone loss appeared to be greater in total knee replacement. Therefore, the aim of the study is to look for any significant difference in medial tibial bone loss in both unicompartmental knee replacement and total knee replacement in the first 3 years and to investigate the underlying pathophysiology. Methods: Cases of fixed-bearing unicompartmental knee replacement and posterior stabilising total knee replacement performed in 2015–2016 were recruited. The change in medial tibial bone loss (expressed in grayscale Gy) over a three-year post-operative period was measured using the method of digital radiological densitometry. Potential predictors and correlations were analysed. Results: Forty-four cases of unicompartmental knee replacement and 52 cases of total knee replacement were recruited. The cumulative drop in 3 years was 23.3% in unicompartmental knee replacement and 33.7% in total knee replacement, respectively, a difference of up to 10%. The cumulative drop between the two groups at 12 months ( p &lt; 0.05) and 36 months ( p &lt; 0.05), respectively, were significantly different. Angle correction has not been shown to affect medial tibial bone loss in this study. No surgical complication was documented during the follow-up period. Conclusion: Total knee replacement results in 10% greater medial tibial bone loss than unicompartmental knee replacement at the three-year time. The effect is greatest in the first year. In addition to possible stress shielding, early physiological bone remodelling in response to surgical trauma can contribute to the difference in medial tibial bone loss of unicompartmental knee replacement and total knee replacement. This is supported by the insignificant correlation between angle correction and medial tibial bone loss in the result.

Fixed-bearing is superior to mobile-bearing in lateral unicompartmental knee replacement: a retrospective matched-pairs analysis

PurposeDue to low incidence of isolated lateral osteoarthritis (OA), there are limited data on whether a fixed-bearing (FB) or a mobile-bearing (MB) design is superior for lateral unicompartmental knee replacement (UKR). The aim of this matched-pairs analysis was to compare both designs in terms of implant survival and clinical outcome.MethodsPatients who received MB-UKR (Group A) and FB-UKR (Group B) at a single centre were matched according to gender, age at time of surgery and body mass index (BMI). Survivorship analysis was performed with the endpoint set as “revision for any reason”. Clinical outcome was assessed using the Oxford knee score (OKS), visual analogue scale for pain (VAS), patients’ satisfaction, University of California Los Angeles activity scale (UCLA) and the Tegner activity score (TAS).ResultsA total of 60 matched pairs were included with a mean follow-up (FU) of 3.4 ± 1.3 (range 1.2–5.0) years in Group A and 2.7 ± 1.2 (range 1.0–5.0) years in Group B. Survivorship between both groups differed significantly (Group A: 78.7%; Group B: 98.3%, p = 0.003) with bearing dislocation being the most common reason for revision in Group A (46.2%). The relative and absolute risk reduction were 92.2% and 20%, respectively, with 5 being the number needed to treat. There were no differences in OKS (Group A: 41.6 ± 6.5; Group B: 40.4 ± 7.7), VAS (Group A: 2.9 ± 3.2; Group B: 1.6 ± 2.2), UCLA (Group A: 5.7 ± 1.3; Group B: 5.9 ± 1.8) and TAS (Group A: 3.0 ± 1.0; Group B: 3.1 ± 1.2) between both groups on follow-up.ConclusionDespite modern prosthesis design and surgical technique, implant survival of lateral MB-UKR is lower than that of FB-UKR on the short- to mid-term due to bearing dislocation as the most common cause of failure. Since clinical results are equivalent in both groups, FB-UKR should be preferred in treatment of isolated lateral OA.Level of evidenceRetrospective case–control study, Level III.

Long-term survivorship and results in lower limb arthroplasty: a registry-based comparison study

IntroductionPopularity of joint replacement surgery due to ever aging population surges the demand for a proper national joint registry. Our Chinese University of Hong Kong – Prince of Wales Hospital (CUHK-PWH) joint registry has passed the 30th year. The aims of this study are 1) summarize our territory-wide joint registry which has passed the 30th year since establishment and 2) compare our statistics with other major joint registries.MethodsPart 1 was to review the CUHK-PWH registry. Demographic characteristics of our patients who underwent knee and hip replacements had been summarized. Part 2 was a series of comparisons with registries from Sweden, UK, Australia and New Zealand.ResultsCUHK-PWH registry captured 2889 primary total knee replacements (TKR) (110 (3.81%) revision) and 879 primary total hip replacements (THR) (107 (12.17%) revision). Median Surgery time of TKR was shorter than THR. Clinical outcome scores were much improved after surgery in both. Uncemented of hybrid in TKR were most popular in Australia (33.4%) and 40% in Sweden and UK. More than half of TKR and THR patients showed the highest percentage with ASA grade 2. New Zealand reflected the best cumulative percentage survival 20 years after surgery of 92.2%, 76.0%, 84.2% survivorship 20 years after TKR, unicompartmental knee replacement (UKR) and Hip.ConclusionA worldwide accepted patient-reported outcome measure (PROM) is recommended to develop to make comparisons among registries and studies feasible. Completeness of registry data is important and useful to improve surgical performance through data comparisons from different regions. Funding from government on sustaining registries is reflected. Registries from Asian countries have yet to be grown and reported.

Setting the Tibial Component Rotation Based on Femoral Landmarks Allows Congruent Knee Kinematics in Robotic-Assisted Medial Unicompartmental Knee Replacement.

The accurate positioning of the prosthetic components is essential for achieving successful results in medial unicompartmental knee arthroplasty (mUKA). The tibial component rotation in image-based robotic-assisted UKA is usually based on tibial bony landmarks matched to the pre-operative CT model. The study aimed to evaluate whether setting the tibial rotation on femoral CT-based landmarks allows congruent knee kinematics. We retrospectively analyzed data from 210 consecutive image-based robotic-assisted mUKA cases. In every case, we set the tibia rotation landmark parallel to the posterior condylar axis and centered it on the trochlea groove defined on the preoperative CT scan. The implant positioning was primarily set parallel to this rotation landmark and then adjusted based on tibial sizes avoiding component over- or under-hang. During surgery, we recorded the knee kinematics under valgus stress to reduce the arthritic deformity. A femoral-tibial contact point was recorded over the entire range of motion and displayed as a tracking profile on the tibia implant. The femoro-tibial tracking angle (FTTA) was then calculated based on a tangent line to the femoro-tibial tracking-points and the difference to the femur-based rotation landmark. In 48% of the cases, we could position the tibia component exactly to the femoral rotation landmark, whereas in 52% of cases, minimal adjustments were made to avoid component's under- or over-hang. The mean tibia component rotation (TRA) with reference to our femur-based landmark was +0.24° (SD ± 2.9°). The femur-based tibia rotation landmark showed a high correspondence to the FTTA with 60% of the cases having less than 1° of deviation. Mean FTTA was +0.7° (SD ± 2.2°). The mean difference between the absolute value of the TRA and the FTTA (|TRA| - |FTTA|) was -0.18° (SD ± 2°). Setting the tibial component rotation based on CT scan femoral landmarks and not on tibial anatomical landmarks is a reliable method to obtain congruent knee kinematics during image-based robotic-assisted medial UKA with less the 2° deviations on average.

The effect of activity on the outcome of cementless mobile bearing unicompartmental knee replacements

BackgroundMany surgeons consider high activity levels a contraindication to Unicompartmental Knee Replacement (UKR). Cementless fixation is of particular concern given the lack of cement to augment primary stability. We assessed the effect of pre and post-operative activity levels on the outcomes of cementless UKRs. MethodsA prospective cohort of 1000 medial cementless mobile bearing UKR were analysed. Patients were categorised by their pre-operative and highest post-operative Tegner Activity Score (TAS) and results compared between groups. Outcomes of interest included implant survival, Oxford Knee Score (OKS) and the American Knee Society Score – Objective/Functional (AKSS-O/F). ResultsIncreasing post-operative activity were not associated with higher revision rates. The 10-year survival of the high activity group (TAS ≥ 5, 96.7% (CI 91.3–98.8), and low/medium activity group (TAS ≤ 4, 98.1% (CI 96.5–99.0)) were not significantly different (p = 0.57). The mean 10-year OKS of the high activity group (46.5, SD 3.1) was significantly (p < 0.001) higher than that of the low/medium activity group (41.3, SD 7.7). There was a significant trend for increasing activity being associated with increasing AKSS-F at 5-years (p < 0.001) and 10 years (p = 0.01) and increasing AKSS-O at 5 years (p < 0.001). Higher pre-operative activity did not significantly increase revision rates and resulted in significantly higher 5-year post-operative scores. ConclusionsNeither higher pre-operative nor post-operative activity were associated with increased revision rates, but both were associated with better post-operative function. Therefore activity should not be considered a contraindication to cementless mobile bearing UKR and not be restricted post-operatively.

Short- to mid-term results of minimally invasive lateral unicompartmental knee replacement: 133 cases in a non-designer series

IntroductionThe aim of the current study was to demonstrate short- to mid-term survivorship as well as clinical outcome of lateral unicompartmental knee replacement (UKR) with a fixed-bearing (FB) design from a non-designer center using the Oxford Fixed Lateral prosthesis.Materials and methodsThis single-center retrospective cohort study reports the results of 133 consecutive lateral FB-UKR. Survivorship analysis was performed with different endpoints and clinical outcome was measured using the Oxford-Knee-Score (OKS), American-Knee-Society-Score (AKSS-O), range-of-motion (ROM) and visual-analog-scale for pain (VAS).ResultsThere were two revision surgeries with conversion to total knee replacements (TKR) due to persistent pain resulting in a survival rate of 98.5% (95% CI 93.5–99.6) with a mean follow-up (FU) of 3.3 ± 1.8 years (range 1–8.5). All outcome scores, VAS and ROM showed a significant improvement at final FU (p < 0.001). The OKS improved from 26 ± 7.8 (range 11–45) preoperatively to 39 ± 8.3 (range 13–48), the AKSS-O from 49.2 ± 14.6 (range 18–90) to 81.8 ± 15.1 (range 40–100), the AKSS-F from 53 ± 23.7 (range 0–100) to 80.4 ± 21.4 (range 5–100) and the ROM from 118 ± 17 (range 90–160) to 134 ± 9.5 (range 100–155).ConclusionsThe short- to mid-term results following lateral FB-UKR demonstrate a high survivorship and good clinical outcome from an independent series. We, therefore, suggest that FB-UKR is a safe treatment option for isolated lateral OA if sufficient surgical experience is provided.Level of evidenceRetrospective cohort study, level IV.

The effect of femoral component valgus/varus angle on the mid-term efficacy of unicondylar knee arthroplasty

ABSTRACT Objective: To investigate the effect of femoral component valgus/varus angle (FCVA) on the mid-term outcome after unicondylar knee arthroplasty. Methods: Patients who underwent unicompartmental knee replacement in the Department of Bone and Joint Surgery, were retrospectively analyzed. According to the postoperative femoral prosthesis internal and external rotation angle, patients were divided into six groups the postoperative femoral prosthesis internal and external rotation angle: standard group, mildly abnormal group. The patients were followed up for 12 months, and complications were recorded during the follow-up period. The Range of motion (ROM), visual analog scale (VAS), and Knee society score (KSS) were compared between the six groups. Results: One hundred twenty-four patients with 124 knees were included in this study. There were no statistical differences in age, gender, body mass index, preoperative ROM, or preoperative VAS, KSS-C, and KSS-F scores among the six groups. Comparison of postoperative outcomes and efficacy grades showed that: (1) the differences in ROM grades, as well as VAS, KSS-C, and KSS-F efficacy at 12 months postoperatively were statistically significant in all six groups by rank sum test; and patients in the normal group had better ROM grades and KSS-F grades than those in the mild and severe abnormality groups; (2) During the follow-up, no patient records had other serious complications such as periprosthetic infection, prosthetic loosening, periprosthetic fracture, and spacer dislocation. Conclusion: Controlling the femoral prosthetic internal rotation angle between 6° and 0° in unicompartmental knee replacements can lead to better mid-term outcomes for patients.