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Orthopaedic Proceedings
Vol. 86-B, Issue SUPP_IV | Pages 446 - 446
1 Apr 2004
Porteous A Hassaballa M Newman J
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Aim: The aim of this study was to evaluate the functional results and ease of performing revision surgery after a primary unicompartmental arthroplasty versus primary total knee arthroplasty. Method: 114 revision TKRs had data collected prospectively as part of our unit’s Knee Database. 45 were revisions of UKR’s and 79 revisions of TKR’s. This data included Bristol Knee Scores (BKS), reason for revision, use of implant augments and bone graft. Measurements were also made of the ability to restore joint-line after revision. Results: In both groups there was a significant improvement in BKS post-operatively. In the UKR group the commonest reason for revision was progression of disease, while in the TKR group it was aseptic loosening. Bone graft was required in significantly fewer UKR cases (20% vs 40%, P< 0.05). Distal femoral augments were used in 45% of the TKR revisions but in none of the revisions from UKR. The joint line was elevated in a significantly higher proportion of revision from TKR cases versus revision from UKR cases (P< 0.001). Revisions from UKR had higher Total BKS and Functional BKS score than revisions from TKR. Conclusions: Revision TKR after a primary UKR requires less bone graft, fewer augments, restores the joint line more frequently and gives improved functional results over revisions after primary TKR


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_I | Pages 99 - 100
1 Mar 2006
Newman J Ackroyd C Evans R
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Introduction. There has been a recent major increase in the use of unicompartmental knee replacement (UKR) but few studies exist comparing its long term efficiency with total knee replacement (TKR). Method. Ethical approval was obtained. Between 1989 and 1992 a randomised prospective study was undertaken in which 102 cases adjudged suitable for UKR were allocated to receive either a St Georg Sled UKR or a Kinematic Modular TKR. Both cohorts had a median age of 68 and a similar sex distribution and preoperative knee score. Regular follow up has been maintained. As reported the early results favoured UKR. All cases have now been assessed after a minimum of 10 years using modified WOMAC, Oxford and Bristol Knee Scores (BKS) as well as radiographs. Results. 28 cases had died with their knees known to be intact, 2 cases were untraceable. 33 knees in each group were reviewed. 3 in each group had been revised, no impending failures were identified on the radiographs. At 10 years the UKR group had better Oxford and WOMAC scores as well as significantly more excellent results (19:14) and fewer fair and poor results on the BKS. Both groups averaged over 105′ of flexion but 61% of the UKR and only 15% of the TKR group had 120′ or more of flexion. Conclusion. The faster rehabilitation and better early results with UKR are maintained for 10 years with few failures occurring. The average BKS of the UKR group only fell from 91 to 88 between 5 and 10 years suggesting minimal evidence of functional deterioration in either the prosthesis or the remainder of the joint


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_III | Pages 376 - 376
1 Jul 2011
Maxwell R
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A cementless version of the Phase 3 Oxford UKR has been used in our unit since mid 2005. We report on our early experience with this implant, reviewing the National Joint Register (NJR) data on UKR in general and Oxford specifically, with respect to six month Oxford Knee Scores (OKS) and revision rates. A single surgeon review of 170 cementless and 132 cemented cases revealed a mean 6 month OKS of 41.5 and revision rate per 100 component years of 0 for the cementless group, and mean 6 month OKS of 40.0 and revision rate of 1.05 for the cemented group. The equivalent results from the NJR for UKR are 38.75 and 1.44. Radiological review of the 170 cementless cases showed no concerns regarding subsidence and encouraging features with respect to ingrowth. There were no radiolucent lines at one year. The cementless components appear to be strongly osteophilic. The NZ experience with the Cementless Oxford is single centre, comprising a small number of high volume surgeons, and the OKS and revision rates are presented. To date, there have been 346 cases with a revision rate per 100 component years of 0.30. In summary, single surgeon and national early experience of the Cementless Oxford UKR from clinical and radiological evidence is encouraging


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_10 | Pages 140 - 140
1 May 2016
Yildirim G Gopalakrishnan A Davignon R Zeller A Pearle A Conditt M
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Introduction. Cementless unicondylar knee implants are intended to offer surgeons the potential of a faster and less invasive surgery experience in comparison to cemented procedures. However, initial 8 week fixation with micromotion less than 150µm is crucial to their survivorship1 to avoid loosening2. Methods. Test methods by Davignon et al3 for micromotion were used to assess fixation of the MAKO UKR Tritanium (MAKO) (Stryker, NJ) and the Oxford Cementless UKR (Biomet, IN). Data was analyzed to determine the activities of daily living (ADL) that generate the highest forces and displacements4, 5. Stair ascent with 3.2BW compressive posterior tibial load was identified to be an ADL which may cause the most micromotion5. Based on previous studies6, 10,000 cycles was set as the run-time. The AP and IE profiles were scaled back to 60% for the Oxford samples to prevent the congruent insert from dislocating. A four-axis test machine (MTS, MN) was used. The largest size UKRs were prepared per manufacturer's surgical technique. Baseplates were inserted into Sawbones (Pacific Research, WA) blocks1. Femoral components were cemented to arbors. The medial compartment was tested, and the lateral implants were attached to balance the loads. Five tests were conducted for each implant with a new Sawbones and insert for each test per the test method3. The ARAMIS System (GOM, Germany) was used to measure relative motion between the baseplate and the Sawbones at three anteromedial locations (Fig. 1). Peak-Peak (P-P) micromotion was calculated in the compressive and A/P directions. FEA studies replicating the most extreme static loading positions for MAKO micromotion were conducted to compare with the physical test results using ANSYS14.5 (ANSYS, PA). Results. MAKO had a maximum axial motion of 36µm (SD=5.28) at gage 2. Oxford had an average gage 1 axial and A/P motion of 109µm (SD=31.77) and 44mm (SD=28.62) respectively (Fig. 2A). FEA correlated well with the MAKO results (Fig. 2B). Discussion. Oxford has been shown to have microseparation in lab testing conditions and the studies by Liddle et al7 under the same stair ascent activity. However, based on our results, MAKO and Oxford are both expected to allow interdigitation for long-term fixation. The Sawbones model does not allow plastic deformation in axial compression and subsequent stabilization, which could allow Oxford to achieve the fixation and clinical success shown in outcome studies. A/P prep for Oxford allows for 3mm gap between the keel and the bone which may explain the variability in the X direction. Distal flatness of the Oxford varied by 0.5mm as shown on Figure 3. The flatness of the boundary of the implant may explain the elevated micromotion observed for Oxford implant. Future studies will concentrate on FEA of manufactured Oxford components to take into account the geometric discrepancies from a perfectly flat model. Davignon et al3 and this study show that the MAKO is expected to achieve long-term fixation in the initial fixation stages similar to the clinically successful Oxford cementless UKR


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_28 | Pages 74 - 74
1 Aug 2013
Jaramaz B Picard F Gregori A
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NavioPFS™ unicondylar knee replacement (UKR) system combines CT-free planning and navigation with robotically assisted bone preparation. In the planning procedure, all relevant anatomic information is collected under navigation, either directly with the point probe or by kinematic manipulation. In addition to key anatomic landmarks and the maps of the articulating surfaces of the femur and tibia, kinematic assessment of the joint laxity is performed. Relative positions of femur and tibia are collected through the flexion/extension range, with the pressure applied to fully stretch the collateral ligament on the operative side. The planning procedure involves three stages: (1) the implant sizing and initial placement,(2) balancing of the gap on the operative side and (3) evaluating the contact points for the recorded flexion data and the planned placement of implants. In the gap balancing stage, the implants are repositioned until they allow for a positive gap, preferably uniform, throughout the entire range of flexion. UKR was planned and prepared on six cadaver knees with the help of NavioPFS system. All knees were normal without any signs of osteoarthritis. Two surgeons have performed medial UKR (4+2), and the bones were prepared using the NavioPFS handheld robotic tool. Postoperatively, we have re-used the data collected during the planning procedure to compare the kinematic (gap balancing) performance of the used implant with three different commercial implant designs. All implants were placed in the orientation recommended by the respective manufacturer, sized to best fit the original bone geometry, and repositioned optimally balance the gap curve through the entire flexion range, without any negative gaps (overlaps). Since these were nonarthritic cadaver knees, the intent was to restore the original preoperative varus/valgus in neutral (zero) flexion. The three implant designs demonstrated variable degree of capability to uniformly balance the knee gap over the entire range of flexion. The first implant (A) required a gap larger than 2 mm in one case out of six, the second (B) was capable of producing the positive gap curve under 2mm of gap in all six cases, and the third (C) required a gap larger than 2 mm in 3 (50%) of cases. All three designs exhibit the reduced gap space in mid (30°–90°) flexion. Despite the best attempts, the artificial implants do not fully replicate the healthy knee kinematics. This is manifested by increased tightness in the mid flexion. In order to balance the gap in mid flexion, additional laxity has to be allowed in full flexion, extension, or both. NavioPFS allows for patient specific planning that takes into account this information, only available intraoperatively. This kind of evaluation on a patient specific basis is a very important planning tool and it allows the insight on the implant performance in mid flexion, typically not available using conventional planning techniques. It can also help in improving kinematic performance of future implant designs


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVIII | Pages 25 - 25
1 Sep 2012
Prud'homme-Foster M Louati H Parai M Dervin G
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Purpose. Unicompartmental knee replacement (UKR) is an established, bone preserving surgical treatment option for medial compartment osteoarthritis (OA). Early revision rates appear consistently higher than those of total knee replacement (TKR) in many case series and consistently in national registry data. Failure with progression of OA in the lateral compartment has been attributed, in part, to surgical technical errors. In this study we used navigation assisted surgery to investigate the effects of improper sizing of the mobile bearing and malrotation of the tibial component on alignment and lateral compartment loading. Method. A total of eight fresh frozen cadaveric lower limbs were used in the study. After thawing overnight, a Brainlab navigation system with an Oxford (Biomet, Inc) medial UKR module was used to capture the native knee anatomy and alignment using a digitizing probe. Following registration, the case was performed with navigation verified neutral cuts and an ideal insert size was selected to serve as a baseline. The bearing thickness was subsequently increased by 2 mm increments to simulate progressive medial joint overstuffing. Excessive tibial internal rotation of 12 was also simulated at each of the intervals. Knee alignment in varus or valgus was recorded in real time for each surgical scenario with the knee in full extension and at 20 of flexion. Lateral compartment peak pressure was measured using a Tekscan pressure map. Results. Incremental overstuffing of the medial compartment with inserts of increasing thickness resulted in a progressive shift to more valgus knee alignment. Internally rotated sagittal cuts at 12 resulted in a further valgus shift for a given insert size. The valgus shift was detectable at full extension however it was more pronounced at 20 of flexion. Conclusion. The intentional technical errors of overstuffing and malrotation in UKR produced coronal valgus knee alignment and a greater load shift to the lateral compartment. These errors can be construed to contribute to the higher early failure rates associated with UKR when compared to TKR. Special care should be taken to ensure a neutral sagittal tibia cut and appropriate bearing selection. The Intra operative verification of knee alignment should be conducted at 20 of flexion where such errors will be easier for the surgeon to detect and rectify


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVIII | Pages 97 - 97
1 Sep 2012
Dervin G Thurston PR
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Purpose. Patients with anterior cruciate ligament (ACL) deficiency and symptomatic medial compartment osteoarthritis (OA) present a challenge in management. These are often younger than typical primary OA patients and aspire to remain athletically active beyond simple ADLs. Combined ACL reconstruction and valgus tibial osteotomy (ACLHTO) is a well documented surgical option for patients deemed wither too young or too active for total knee arthroplasty. Unicompartmental knee arthroplasty (UKA) is an established surgical treatment for symptomatic medial osteoarthritis of the knee refractory to conservative management. A commonly cited contraindications is symptomatic ACL deficiency because of previous reports detailing premature failure through loosening of the tibial component. Improved results and endoscopic ACL reconstructive procedures have led to an enticing concept of combining ACL reconstruction with medial unicompartmental knee arthroplasty (ACLUKR) for those ACL-deficient medial osteoarthritic (OA) knees. We sought to compare the outcomes in 2 cohorts of patients who underwent either ACLHTO or ACLUKR for this clinical problem. Method. Patients presenting with symptomatic bone on bone medial compartment OA and concomitant ACL deficiency (clinical or asymptomatic) were evaluated for surgery after exhausting non operative management. Patients who were under 40 or had plans to return to high impact loading sports and/or who had more moderate OA were offered combined ACL – medial opening wedge tibia osteotomy as a surgical procedure of choice. Patients were considered for combined ACL Oxford replacement if they were primarily seeking pain relief and were not engaged or aspiring to return to high impact or pivoting sports. All cases but one were concurrent ACL with either HTO or UKR with autogenous hamstring grafts used in all but 2 cases. Results. Thirty of 34 consecutive cases were available for follow-up for a rate of 88%. The median ages for 14 cases of ACLUKR was 51 (range 43 60) whereas 16 patients with ACLHTO had median age 43.4 (range 32 −59). Median FU was 4.65 yrs with minimum 2 year follow up (range 2–8.3). Three of the cases were revision ACL cases all from previous Gore-Tex reconstructions. All but the first patient had concomitant ACL and Oxford unicompartmental knee replacement at 1 surgical sitting and are the subject of this report. The first patient had an autogenous patella bone tendon bone graft performed 6 months prior to the UKA. There were similar change scores for patients in both groups. For ACLUKR, WOMAC pain improvements from 48.1 10.2 SD preoperatively to 79.0 17 SD postop. For ACLHTO, WOMAC improvements from 55.1 13.2 SD preoperatively to 85.0 17 SD postop. To date there have been no cases of infection or bearing dislocation in the ACLUKR group. One patient in the ACLHTO group was revised to TKR for ongoing pain and postoperative flexion contracture. Patient activities ranged from ambulation to vigorous hiking, tennis, and downhill skiing in the UKR group whereas a few in the ACLHTO group were also running mid distances. Overall satisfaction was similar in both groups. Conclusion. ACL reconstruction can safely be combined with medial UKR. The procedure has been used in younger patients with a view toward bone preservation while anticipating need for future revision. Both cohorts showed similar improvements and can be considered. The choice should be geared toward patient athletic demand. While short term results are encouraging though longer term data are necessary to thoroughly evaluate the role of this procedure in patients with medial compartment osteoarthritis and ACL deficiency


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XVIII | Pages 12 - 12
1 May 2012
Simpson DJ Kendrick B Price AJ Murray D Gill H
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Introduction. Unicompartmental Knee Replacement (UKR) is an appealing alternative to Total Knee Replacement (TKR) when the patient has isolated compartment osteoarthritis (OA). A common observation post-operatively is radiolucency between the tibial tray wall and the bone. In addition, some patients complain of persistent pain following implantation with a UKR; this may be related to elevated bone strains in the tibia. The aim of this study was to investigate the mechanical environment of the tibia bone adjacent to the tray wall, following UKR, to determine whether this region of bone resorbs, and how altering the mechanical environment affects tibia strains. Materials and methods. A finite element (FE) model of a cadaver tibia implanted with an Oxford UKR was used in this study, based on a validated model. A single static load, measured in-vivo during a step-up activity was used. There was a 1 mm layer of cement surrounding the keel in the cemented UKR, and the cement filled the cement pocket. In accordance with the operating procedure, no cement was used between the tray wall and bone. For the cementless UKR a layer of titanium filled the cement pocket. An intact tibia was used to compare to the cemented and cementless UKR implanted tibiae. The tibia was sectioned by the tray wall, defining the radiolucency zone (parallel to the vertical tray wall, 2 mm wide with a volume of 782.5 mm. 3. ), corresponding to the region on screened x-rays where radiolucencies are observed. Contact mechanics algorithms were used between all contacting surfaces; bonded contact was also introduced between the tray wall and adjacent bone, simulating a mechanical tie between them. Strain energy density (SED), was compared between the intact and implanted tibia for the radiolucency zone. Equivalent strains were compared on the proximal tibia between the intact and implanted tibia models. Forty patients (20 cemented, 20 cementless) who had undergone UKR were randomly selected from a database, and assessed for radiolucency. Results. The SED in the radiolucency zone was 80% lower in the cemented and cementless tibia, compared to the intact tibia, without a mechanical tie between the tibial tray wall and adjacent bone. When a mechanical tie was introduced the SED in the radiolucency zone was 35% higher in the cemented and cementless tibia, compared to the intact tibia. The strain on the proximal tibia was reduced by 20% when a mechanical tie was used between the tray wall and adjacent bone. Radiolucency at the tray wall was observed in all forty radiographs examined. Discussion. This work has presented a static snapshot of the load being carried through the proximal tibia following implantation with an Oxford UKR. It has been shown that by introducing a mechanical tie between the tibial tray wall and the adjacent bone, the SED in the region observed to have radiolucency is increased; this has the potential of reducing the likelihood of a radiolucency occurring in that region. Moreover, the strain observed in the proximal tibia was reduced when a mechanical tie was introduced, which may reduce the incidence of pain following implantation with a UKR. It is recommended that integration between the bone and the tray wall is important for UKR


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_I | Pages 47 - 48
1 Mar 2009
van Duren B Gallagher J Pandit H Beard D Dodd C Gill H Murray D
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Introduction: The Oxford unicompartmental knee replacement (UKR) use in the lateral compartment has been associated with a reduced flexion range and increased medial compartment pain than seen with its medial counterpart due to, in part, the inadequacy of a flat tibial tray replacing the domed anatomy of the lateral tibia. A new design incorporating a domed tibial component and a biconcave meniscal bearing has been developed to overcome these problems. This study reports a clinical comparison of new and old establishing whether this modified implant has maintained the established normal kinematic profile of the Oxford UKR. Method: Patients undergoing lateral UKR for OA were recruited for the study. Fifty one patients who underwent UKR with the domed design were compared to 60 patients who had lateral UKR with a flat inferior bearing surface. Kinematic evaluation was performed on 3 equal subgroups (n = 20); Group 1-Normal volunteer knees, Group 2-Flat Oxford Lateral UKR’s and Group 3-Domed Oxford Lateral UKR’s. The sagittal plane kinematics of each knee was assessed using videofluoroscopic analysis whilst performing a step up and deep knee bend activity. The fluoroscopic images were recorded digitally, corrected for distortion using a global correction method and analysed using specially developed software to identify the anatomical landmarks needed to determine the Patella Tendon Angle (PTA) (the angle the patella tendon and the tibial axis). Knee kinematics were assessed by analysing the movement of the femur relative to the tibia using the PTA. Results: PTA/KFA values, for both devices, from extension to flexion did not show any significant difference in PTA values in comparison to the normals as measured by a 3-way ANOVA. The Domed implant achieved higher maximal active flexion during the lunge exercise than those with a flat implant. Only 33% of the flat UKR’s achieved KFA of 130° or more under load whilst performing a lunge, compared with 75% of domed UKR’s and 90% of normal knees. No flat UKR achieved a KFA of 140° or more, yet 50% of all domed UKR’s did, as did 60% of all normal knees. Conclusions: There was no significant difference in sagittal plane kinematics of the domed and flat Oxford UKR’s. Both designs had favorable kinematic profiles closely resembling that of the normal knee, suggesting normal function of the cruciate mechanism. The domed knees had a greater range of motion under load compared to the flats, approaching levels seen with the normal knee, suggesting that limited flexion for the flat plateau results from over tightening in high flexion and that this is corrected with the domed plateau. Problems with the second generation of lateral Oxford UKA have been rectified by a new bi-concave bearing without losing bearing stability and normal kinematics


The Bone & Joint Journal
Vol. 95-B, Issue 10 | Pages 1348 - 1353
1 Oct 2013
Valenzuela GA Jacobson NA Buzas D Korecki TD Valenzuela RG Teitge RA

The outcome of high tibial osteotomy (HTO) deteriorates with time, and additional procedures may be required. The aim of this study was to compare the clinical and radiological outcomes between unicompartmental knee replacement (UKR) and total knee replacement (TKR) after HTO as well as after primary UKR. A total of 63 patients (63 knees) were studied retrospectively and divided into three groups: UKR after HTO (group A; n = 22), TKR after HTO (group B; n = 18) and primary UKR (group C; n = 22). The Oxford knee score (OKS), Knee Society score (KSS), hip–knee–ankle angles, mechanical axis and patellar height were evaluated pre- and post-operatively. At a mean of 64 months (19 to 180) post-operatively the mean OKS was 43.8 (33 to 49), 43.3 (30 to 48) and 42.5 (29 to 48) for groups A, B and C, respectively (p = 0.73). The mean KSS knee score was 88.8 (54 to 100), 88.11 (51 to 100) and 85.3 (45 to 100) for groups A, B and C, respectively (p = 0.65), and the mean KSS function score was 85.0 (50 to 100) in group A, 85.8 (20 to 100) in group B and 79.3 (50 to 100) in group C (p = 0.48). Radiologically the results were comparable for all groups except for patellar height, with a higher incidence of patella infra following a previous HTO (p = 0.02). Cite this article: Bone Joint J 2013;95-B:1348–53


The Bone & Joint Journal
Vol. 95-B, Issue 8 | Pages 1064 - 1068
1 Aug 2013
Cavaignac E Lafontan V Reina N Pailhé R Warmy M Laffosse JM Chiron P

The significance of weight in the indications for unicompartmental knee replacement (UKR) is unclear. Our hypothesis was that weight does not affect the long-term rate of survival of UKRs. We undertook a retrospective study of 212 UKRs at a mean follow-up of 12 years (7 to 22). The patients were distributed according to body mass index (BMI; < vs ≥ 30 kg/m. 2. ) and weight (< vs ≥ 82 kg). Kaplan-Meier survivorship analysis was performed and ten-year survival rates were compared between the sub-groups. Multimodal regression analysis determined the impact of the various theoretical contraindications on the long-term rate of survival of UKR. The ten-year rates of survival were similar in the two weight subgroups (≥ 82 kg: 93.5% (95% confidence interval (CI) 66.5 to 96.3); < 82 kg: 92.5% (95% CI 82.5 to 94.1)) and also in the two BMI subgroups (≥ 30 kg/m. 2. : 92% (95% CI 82.5 to 95.3); < 30 kg/m. 2. : 94% (95% CI 78.4 to 95.9)). Multimodal regression analysis revealed that weight plays a part in reducing the risk of revision with a relative risk of 0.387, although this did not reach statistical significance (p = 0.662). The results relating weight and BMI to the clinical outcome were not statistically significant. Thus, this study confirms that weight does not influence the long-term rate of survival of UKR. Cite this article: Bone Joint J 2013;95-B:1064–8


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 490 - 490
1 Sep 2012
Confalonieri N Manzotti A
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Introduction. The authors performed a short term prospective study of unicompartmental knee replacement (UKR) associated to patella-femoral arthroplasty (PFA) for the treatment of bicompartmental symptomatic knee arthritis. At the latest follow-up all the implants were matched to a similar computer assisted Total Knee Replacements (CAS-TKR) group implanted for the same indications. Hypothesis of the study was that this bicompartimental implants could achieve comparable outcomes to TKR with a more conservative surgery and a higher joint function. Materials and Methods. 19 cases of anteriomedial (12) or anterolateral (7) arthritis in 19 stable knees were prospectively involved in the study. All the knees underwent to a selective reconstruction using simultaneously both UKR and PFR using the same surgical technique. All bicompartmental implants were performed by the same surgeon. Surgical time, hospital staying and all intra and post operative complications were registered. At a minimum follow-up of 20 months, every single case was marched to a similar case where had been implanted a computer assisted cruciate retaining TKR. Criteria of matching were: sex, age, pre-operative range of motion and arthritis grade. In both the groups all the cases were assessed clinically using WOMAC, KKS and GIUM scores. All the knees were radiologically investigated using the same radiological protocol. Results. Intra operatively we did not registered any complication. No revision in both groups. The mean surgical time was 86 minutes (range: 78–121) in UKR+PFR group and 81 minutes (range: 71–112) in CAS-TKR group. There were no statistical significant differences in the hospital stay. No statistically significant difference was seen for the Knee Society, Functional and GIUM scores between the 2 groups. Statistically significant better WOMAC Function/Stiffness indexes were registered for the UKR+PFR group. CAS-TKR implants achieved a statistically better aligned mechanical axes. Conclusions. The results of this prospective short term prospective study suggest that UKR+PFR implant is a viable option for bicompartmental anteromedial arthritis at least as well as TKR but maintaining an higher level of function


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 144 - 144
1 Sep 2012
Bruni D Raspugli G Iacono F Lo Presti M Zaffagnini S Marcacci M
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Background. The reported outcomes of unicompartmental knee replacement (UKR) for spontaneous osteonecrosis of the knee (SPONK) often derive from small series with an average followup of 5 years, enabling to generate meaningful conclusions. Therefore, we determined the long-term functional results and the 10-years survivorship of the implant in all patients with advanced SPONK of the medial tibio-femoral compartment treated with a unicompartmental knee arthroplasty at our institute. Methods. We retrospectively evaluated 84 consecutive patients with late stage SPONK. All patients received a pre-operative MRI to confirm the diagnosis, to exclude any metaphyseal involvement and to assess the absence of significative degenerative changes in the lateral and PF compartment. Mean age at surgery was 66 years and mean body mass index (BMI) was 28.9. In all cases, SPONK involved the medial compartment; in 77 cases the medial femoral condyle (MFC) was involved, while in 7 cases the pathology site was the medial tibial plateau (MTP). Radiological evaluation was conducted by 3 different radiologists and clinical evaluation according to KSS and WOMAC score was performed by 3 fellows from outside institutions, with no previous clinical contact with the patients, at a mean followup of 98 months. Results. We found a significant improvement in VAS score for residual pain self-assessment and maximum knee flexion (p<0.0001). The 10-year Kaplan-Meier survivorship with revision for any reason as endpoint was 89%. Mean results at final observation point for global KSS and WOMAC score were 87.1 (range 45–100; standard deviation 13.8) and 12 (range 0–44; standard deviation 10.3), respectively. No patient had significant radiographic signs of osteoarthritis progression in the lateral compartment or in the patello-femoral compartment at final evaluation. Conclusions. Our findings suggest that medial UKR performed for late stage SPONK of the medial tibio-femoral compartment in selected patients provides satisfactory long term clinical and radiographical results, with a 10-years Kaplan-Meier survivorship of the implant of 89%


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XL | Pages 78 - 78
1 Sep 2012
Jaramaz B Nikou C
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Introduction

Precision Freehand Sculpting(PFS), is a hand-held semi-active robotic technology for bone shaping that works within the surgical navigation framework. PFS can alternate between two control modes – one based on control of exposure of the cutting bur (“Exposure Control”) and another based on the control of the speed of the cutting bur (“Speed Control”). In this study we evaluate the performance of PFS in preparing the femoral bone surface for unicondylar knee replacement (UKR).

Methods

The experiment is designed to prepare a synthetic bone for unicondylar knee replacement (UKR). The implant plan is mapped to individual specimen using a jig that fit in a unique and repeatable way to all specimens. During bone preparation, the PFS handpiece and the specimen are both tracked with the Polaris Spectra (Northern Digital Inc.) using passive reflective markers. The cutting plan is specified so that the specimens can receive a specially designed implant after the cut is finished. The implant is a modified commercial design with three planar back faces and two pegs. In addition there are 10 conical divots on the implant surface that can be used to register the implant after it is placed on the prepared bone surface. The distal and distal-anterior facets were cut with a 5 mm cylindrical bur using Extension Control. The posterior facet and the post holes were cut using 6 mm spherical bur using Speed Control.

Three subjects cut 5 specimens each. One subject was an experienced PFS user. The second user was somewhat less experienced, and the third user was completely inexperienced with the use of PFS. The performance was evaluated in terms of the implant fit and the performance time. The final implant fit was characterized using a MicroScribe MX desktop coordinate measuring arm.


The Journal of Bone & Joint Surgery British Volume
Vol. 94-B, Issue 10 | Pages 1321 - 1329
1 Oct 2012
Sarmah SS Patel S Hossain FS Haddad FS

Radiological assessment of total and unicompartmental knee replacement remains an essential part of routine care and follow-up. Appreciation of the various measurements that can be identified radiologically is important. It is likely that routine plain radiographs will continue to be used, although there has been a trend towards using newer technologies such as CT, especially in a failing knee, where it provides more detailed information, albeit with a higher radiation exposure.

The purpose of this paper is to outline the radiological parameters used to evaluate knee replacements, describe how these are measured or classified, and review the current literature to determine their efficacy where possible.


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_11 | Pages 11 - 11
7 Jun 2023
McNamara J Eastman J Perring A Vallance N Frigyik A Pollalis A
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The development and implementation of Enhanced Recovery After Surgery (ERAS) protocols are of particular interest in elective orthopaedics due to clinical benefits and cost effectiveness. The Wycombe Arthroplasty Rapid-Recovery Pathway (WARP) was designed to streamline hip and knee joint arthroplasty to reduce time spent in hospital whilst optimising outcomes in an NHS District General Hospital. 966 patients were admitted to Wycombe General Hospital for primary elective joint replacement (60 UKR, 446 THR, 460 TKR) during the period 1st September 2020 to 31st September 2022. The WARP pathway was used for 357 (37%) patients (32 UKR, 155 THR, 170 TKR) and the standard “non-WARP” pathway was used for 609 (63%) patients (28 UKR 291 THR, 290 TKR). Data was collected on length of stay, time of mobilisation, number of physiotherapy sessions, and inpatient morbidity. Average length of stay following UKR was 0.75 days for WARP vs 2.96 for non-WARP patients, following THR was 2.17 days for WARP vs 4.17 for non-WARP patients, following TKR was 3.4 days for WARP vs 3.92 for non-WARP patients. Day-0 mobilisation after UKR was achieved in 97% of WARP vs 12% of non-WARP patients, after THR in 43% of WARP vs 14% of non-WARP patients, after TKR in 33% of WARP vs 11% of non-WARP patients. Same-day discharge was achieved in the WARP cohort in 63% of UKR, 10% of THR, 2% of TKR patients. There were no same-day discharges in the non-WARP cohort. Complications delaying mobilisation (pain, nausea/vomiting, dizziness/low BP) were identified in 8.4% of WARP vs 25% of non-WARP patients. Our cohort study shows that the initiation of WARP Rapid Recovery pathway for joint arthroplasty decreased the average length of stay after UKR by 2.21 days, after THR by 2 days, after TKR by 0.52 days. Time to first mobilisation was decreased significantly by increased rates of same-day mobilisation and reduced rates of postoperative anaesthetic-related complications


Abstract. Introduction. Medial fix bearing unicompartmental knee replacement (UKR) designs are consider safe and effective implants with many registries data and big cohort series showing excellent survivorship and clinical outcome comparable to that reported for the most expensive and surgically challenging medial UKR mobile bearing designs. However, whether all polyethylene tibial components (all-poly) provided comparable results to metal-backed modular components during medial fix bearing UKR remains unclear. There have been previous suggestions that all-poly tibia UKR implants might show unacceptable higher rates of early failure due to tibial component early loosening especially in high body max index (BMI) patients. This study aims to find out the short and long-term survival rate of all-poly tibia UKR and its relationship with implant thickness and patient demographics including sex, age, ASA and BMI. Material and Methods. we present the results of a series of 388 medial fixed bearing all-polly tibia UKR done in our institution by a single surgeon between 2007–2019. Results. We found out excellent implant survival with this all-poly tibia UKR design with 5 years survival rate: 96.42%, 7 years survival rate: 95.33%, and 10 years survival rate: 91.87%. Only 1.28% had early revision within 2 years. Conclusion. Fixed bearing medial all-poly tibia UKR shows excellent survivor rate at 2, 5, 7 and 10 years follow up and the survival rate is not related with sex, age, BMI, ASA grade or implant thickness. Contrary to the popular belief, we found out that only 1.71% of all implants was revised due to implant loosening


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 31 - 31
7 Aug 2023
Myatt D Marshall M Ankers T Robb C
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Abstract. Unicompartment knee replacement (UKR) has been an effective treatment of isolated medial compartment osteoarthritis (OA). There has been several studies which suggest that patellofemoral (PFJ) wear may not be a relative contraindication for UKR with no statistical difference in failure rates. There is currently conflicting evidence on the role of BMI. We will review if BMI and PFJ wear impacts on the post operative functional scores following UKR. A retrospective review of a prospectively collected database was performed. Data was collected between 26/6/2014 and 25/8/2022. 159 UKR procedures were identified. BMI and PFJ cartilage wear were collected. Oxford knee scores (OKS) were collected at > 2 years. PFJ wear was split into International Cartilage Research Society (ICRS) grades I&II and III&IV. 159 UKR procedures were identified, of these 115 had 2 year follow up. There were 77 who had OKS recorded at 2 years. For PFJ wear there was no statistical difference in the median OKS at 2 years 45 vs 43.5 (p=0.408). Assessing the BMI the median was 29kg/m. 2. , range 20–43kg/m. 2. Spearman's rank was performed to assess the correlation between BMI and >2 year OKS, this demonstrated a moderately negative correlation p(df)=−0.339 (CI 95% −0.538, −0.104) p=0.004. There is no statistically significant difference in >2 year OKS following UKR regardless of PFJ wear. There is a moderately negative correlation between BMI and >2 year OKS which was significant p=0.004. Therefore BMI is a more important consideration when counselling patients for UKR


Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_8 | Pages 3 - 3
10 May 2024
Hancock D Leary J Kejriwal R
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Introduction. This study assessed outcomes of total knee joint replacements (TKJR) in patients who had undergone previous periarticular osteotomy compared with unicompartmental knee replacement (UKR). Establishing a difference in the results of total knee joint replacements following these operations may be an important consideration in the decision-making and patient counselling around osteotomy versus UKR for the management of single-compartment osteoarthritis. Method. Using data from the New Zealand Joint Registry, we identified 1,895 total knee joint replacements with prior osteotomy and 1,391 with prior UKR. Revision rates and patient-reported outcomes, as measured by the Oxford Knee Score (OKS), between these two groups were compared. Adjusted hazard ratios were also calculated to compare the groups. Results. The revision rate for total knee joint replacement following osteotomy was significantly lower than TKJR following UKR (0.88 per 100 component years versus 1.38 per 100 component years, respectively). Adjusted hazard ratio calculations found that those with TKJR with prior UKR had more than double the risk of requiring revision than those with prior osteotomy. Additionally, there was a statistically significant difference in the mean adjusted OKS scores between the two groups, with improved outcomes in the group with prior osteotomy. Conclusion. Our findings suggest that total knee joint replacement following periarticular osteotomy have a lower risk of revision and improved OKS when compared to those with prior UKR. Previous studies assessing New Zealand Joint Registry have not found a statistically significant difference between the two groups however, these results are no longer in keeping with more contemporary literature. Our study confirms the New Zealand population to be comparable with international studies with TKJR after osteotomy performing significantly better compared with prior UKR


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_3 | Pages 102 - 102
23 Feb 2023
Campbell T Hill L Wong H Dow D Stevenson O Tay M Munro JT Young S Monk AP
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Contemporary indications for unicompartmental knee replacement (UKR) include bone on bone radiographic changes in the medial compartment with relatively preserved lateral and patellofemoral compartments. The role of MRI in identifying candidates for UKR is commonplace. The aim of this study was to assess the relationship between radiographic and MRI pre-operative grade and outcome following UKR. A retrospective analysis of medial UKR patients from 2017 to 2021. Inclusion criteria were medial UKR for osteoarthritis with pre-operative and post-operative Oxford Knee Scores (OKS), pre-operative radiographs and MRI. 89 patients were included. Whilst all patients had grade 4 ICRS scores on MRI, 36/89 patients had grade 3 KL radiographic scores in the medial compartment, 50/89 had grade 4 KL scores on the medial compartment. Grade 3 KL with grade 4 IRCS medial compartment patients had a mean OKS change of 17.22 (Sd 9.190) meanwhile Grade 4 KL had a mean change of 17.54 (SD 9.001), with no statistical difference in the OKS change score following UKR between these two groups (p=0.873). Medial bone oedema was present in all but one patient. Whilst lateral compartment MRI ICRS scores ranged from 1 to 4 there was no association with MRI score of the lateral compartment and subsequent change in oxford score (P value 0.458). Patellofemoral Compartment (PFC) MRI ICRS ranged from 0 to 4. There was no association between PFC ICRS score and subsequent change in oxford knee score (P value .276). Radiographs may under report severity of some medial sided knee osteoarthritis. We conclude that in patients with grade 3 KL score that would normally not be considered for UKR, pre-operative MRI might identify grade 4 ICRS scores and this subset of patients have equivalent outcomes to patients with radiographic Grade 4 KL medial compartment osteoarthritis


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_2 | Pages 60 - 60
10 Feb 2023
Daly D Maxwell R
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The purpose of this study is to assess the long term results of combined ACL reconstruction and unicompartmental knee replacements (UKR). These patients have been selected for this combined operation due to their combination of instability symptoms from an absent ACL and unicompartmental arthritis. Retrospective review of 44 combined UKR and ACL reconstruction by a single surgeon. Surgeries included both medial and lateral UKR combined with either revision ACL reconstruction or primary ACL reconstruction. Patient reported outcomes were obtained preoperatively, at one year, 5 years and 10 years. Revision rate was followed up over 13 years for a mean of 7.4 years post-surgery. The average Oxford score at one year was 43 with an average increase from pre-operation to 1 year post operation of 15. For the 7 patients with 10 year follow up average oxford score was 42 at 1 year, 43 at 5 years and 45 at 10 years. There were 5 reoperations. 2 for revision to total knee arthroplasty and 1 for an exchange of bearing due to wear. The other 2 were the addition of another UKR. For those requiring reoperation the average time was 8 years. Younger more active patients presenting with ACL deficiency causing instability and unicompartmental arthritis are a difficult group to manage. Combining UKR and ACL reconstruction has scant evidence in regard to long term follow up but is a viable option for this select group. This paper has one of the largest cohorts with a reasonable follow up averaging 7.4 years and a revision rate of 11 percent. Combined unilateral knee replacements and ACL reconstruction can be a successful operation for patients with ACL rupture causing instability and unicompartmental arthritis


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_9 | Pages 19 - 19
1 Oct 2020
Murray DW
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Background. There are advantages and disadvantages of Unicompartmental (UKR) and Total Knee Replacement, with UKR having better functional outcomes with fewer complications but a higher revision rate. The relative merits depend on patient characteristics. The aim was to compare UKR and TKR risk-benefits and cost-effectiveness in patients with severe systemic morbidity. Methods. Data from the National Joint Registry for England, Wales and Northern Ireland was linked to hospital inpatient and patient-reported outcomes data. Patients with American Society of Anesthesiologists (ASA) grade ≥3 undergoing UKR or TKR were identified. Propensity score stratification was used to compare 90-day complications and 5-year revision and mortality of 2,256 UKR and 57,682 TKR, and in a subset of 145 UKR and 23,344 TKR Oxford Knee Scores (OKS). A health-economic analysis was based on EQ-5D and NHS hospital costs. Results. The OKS was significantly better following UKR than TKR with a difference of 1.83 (95%CI 0.10–3.56). UKR was associated with lower relative risks of venous thromboembolism (0.33, CI0.15–0.74), myocardial infarction (0.73, CI0.36–1.45) and early joint infection (0.85, CI0.33–2.19) but only the decrease in venous thromboembolism was significant. The revision risk following UKR was significantly higher than following TKR (hazard ratio 2.70, CI2.15–3.38) and the mortality was significantly lower (0.52, CI0.36–0.74). At five years the cumulative incidence of revision was 8% higher with UKR, and the cumulative incidence of death was 13% lower. The health economic analysis found that UKR dominated TKR having lower costs (£359, CI340-378) and higher quality-of-life gains (0.33, CI-0.31–0.970). Conclusions. For patients with ASA ≥3, UKR was safer and more cost-effective than TKR. In particular if UKR was used instead of TKR the number of lives saved was higher than the number of extra revisions. UKR should be considered the first option for suitable patients with severe co-morbidity


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 35 - 35
7 Aug 2023
Saghir R Aldridge W Metcalf D Jehan S Ng A
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Abstract. Introduction. Uni-compartmental knee replacement (UKR) has become popularised due to quicker recovery times, reduced postoperative pain, and blood loss. The desire to increase bed capacity and reduce costs, while preserving safety and patient satisfaction, has led to increased interest in day-case arthroplasty. This study observes the feasibility of UKR as a day-case procedure and whether this affects short and long-term postoperative outcomes. Methodology. Between 2018 and 2021, at a single institution and operated by a single orthopaedic surgeon, seventy-seven patients received a UKR on an elective basis. The patients were divided into two groups: ‘day-case’ for those discharged on the same day, and ‘non day-case’ group. Results. 31 patients were identified as day case procedures with the remaining 46 requiring between one to three days before discharge. Mean age, sex, modal ASA score, BMI, Charlson co-morbidity index, and pre-op oxford knee score showed no statistically significant difference between the two groups (p>0.05). No significant difference between the post-op oxford knee score at 1 year was found for patients treated and discharged as a day case procedure (37.8 +/− 6.88) and those who remained as an inpatient postoperatively (37.8 +/− 10.7); t(df) = −0.0007, p=0.994. No patients in either group suffered any complications beyond the peri-operative period. 30-day and 90-day readmission rates were equal. Conclusions. With no significant differences in post-op knee scores, complication, and readmission rates, we feel UKR can be performed as a viable day case procedure in a planned elective setting. This will result in significant cost savings


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_3 | Pages 53 - 53
23 Feb 2023
Gregor R Hooper G Frampton C
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Due to shorter hospital stays and faster patient rehabilitation Unicompartmental Knee Replacements (UKR) are now considered more cost effective than Total Knee Joint Replacements (TKJR). Obesity however, has long been thought of as a relative contraindication to UKR due to an unproven theoretical concern of early loosening. This study is a retrospective review of patient reported outcome scores and revision rates of all UKR with recorded BMI performed by the Canterbury District Health Board (CDHB) from January 2011 and September 2021. Patient reported outcome scores were taken preoperatively, at 6 months, 1 year, 5 years and 10 years post operatively. These included WOMAC, Oxford, HAAS, UCLA, WHOQOL, normality, pain and patient satisfaction. 873 patients had functional scores recorded at 5 years and 164 patients had scores recorded at 10 years. Further sub-group analysis was performed based on patient BMI of <25, 25–30, 30–35 and >35. Revision data was available for 2377 UKRs performed in Christchurch during this period. Both obese (BMI >30) and non-obese (BMI <30) patients had significantly improved post-operative scores compared to preoperative. Pre-operatively obese patients had significantly lower functional scores except for pain and UCLA. All functional scores were lower in obese patients at 5 years but this did not meet minimum clinical difference. At 10 years, there was significantly lower HAAS, satisfaction and WOMAC scores for obese patients but no difference in Oxford, normality, WHOQOL, UCLA and pain scores. There was no significant difference in the improvement from pre-operative scores between obese and non-obese patients. All cause revision rate for obese patients at 10 years was 0.69 per 100 observed component years compared to 0.76 in non-obese. This was not statistically significant. Our study proves that UKR is an excellent option in obese patients with post-operative improvement in functional scores and 10 year survivorship equivalent to non-obese patients


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_7 | Pages 84 - 84
1 Jul 2022
Rahman A Dangas K Mellon S Murray D
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Abstract. Introduction. After remodelling, loss of bone density beside the keel of cementless UKR tibial components has been observed as a potential cause of concern. How this affects patient-reported outcomes, and further clinical implications, is unclear. This study aims to assess the effect of cementless UKR implantation on tibial bone density, and to explore its relationship to patient demographics and outcomes. Method. This prospective study assesses 115 anterior-posterior radiographs from cementless UKR postoperatively and five years after surgery. Grey values from nine regions around each keel were collected and standardised to enable inter-radiograph comparison. Change between the post-operative and 5-year radiographs (indicating bone density) was calculated, and effect on 5-year patient demographics and pain and functional outcomes was assessed. Repeat measurements were performed by two operators to assess reliability. Results. There was excellent inter-operator correlation. There was increased bone density directly below the keel (9.1% vs 3.3%: p<0.0001), and reduced density beside the keel (−5.9% vs -1.0%, p<0.0001); comparisons to adjacent regions. Overall remodelling was significantly greater in smaller tibias (p=0.006), and females (p=0.01). Remodelling was unrelated to outcomes (OKS, ICOAP-A/B, TAS), age, and BMI. Conclusion. Remodelling patterns suggest increased loading below and decreased loading adjacent to the tibial keel. Remodelling is greater in smaller tibias and females. Remodelling is not related to any patient-reported pain or function five years after surgery, suggesting that remodelling is successful in removing any mechanical source of bone pain. Therefore, clinicians viewing such remodelling patterns can ignore them as they are of no consequence


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_11 | Pages 6 - 6
1 Oct 2019
Masri BA Zamora T Garbuz DS Greidanus NV
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Introduction. The number of medial unicompartmental knee replacements (UKR) performed for arthritis has increased and as such, revisions to total knee replacement (TKR) is increasing. Previous studies have investigated survivorship of UKR to TKR revision and functional outcomes compared to TKR to TKR revision, but have failed to detail the surgical considerations involved in these revisions. Our objectives are to investigate the detailed surgical considerations involved in UKR to TKR revisions. Methods. This study is a retrospective comparative analysis of a prospectively collected database. From 2005 to 2017, 61 revisions of UKR to TKR were completed at a single center. Our inclusion criteria included: revision of UKR to TKR or TKR to TKR with minimum 1 year follow-up. Our exclusion criteria include: single component and liner revisions and revision for infection. The 61 UKR to TKR revisions were matched 2:1 with respect to age, ASA and BMI to a group of 122 TKR to TKR revisions. The following data was collected: indication for and time to revision, operative skin to skin surgical time, the use of specialized equipment (augment size/location, stem use), intraoperative and postoperative complications, re-operations and outcome scores (WOMAC, Oxford 12, SF 12, satisfaction score). Results. There were no statistical differences between the demographic data from either group (age, BMI, ASA, sex and follow-up range). Progression of arthritis was the most common reason for revision in the UKR to TKR group (30/61, 49%, p < 0.001). Aseptic loosening was the most common reason for revision in the TKR to TKR group (73/122, 60%,) and was encountered more often than aseptic loosening in the UKR to TKR group (21/61, 35%, p=0.002). The operative time was longer in the TKR to TKR group (77 vs 112 min, p< 0.001). Femoral augmentation was required for one 1/61 (1.64%) UNI and 92/122 (75%) TKR revisions, respectively (p <0.001). Medial tibial augments were required in 9/61 (14.8%) of the UKR to TKR group while 12/122 (10%) and 10/122 (8%) of the TKR to TKR group required medial and full tibial augments, respectively (p=0.7). UKR to TKR revisions never required femoral stems while 120/122 (98%) of the TKR to TKR group did (p<0.001). Tibial stems were required in 19/61 (31%) and 122/122 (100%) of UKR to TKR and TKR to TKR groups, respectively (p<0.001). There was no statistical difference in the overall complication rate of either group (15% in the UKR to TKR group and 13% in the TKR to TKR group, p = 0.9). Stiffness was a common complication of UKR to TKR and TKR to TKR re-revisions at 2/61 (3%), and 6/122 (5%), respectively (P = 0.6). Aseptic loosening was also a common complication of in both groups at 2/61 (3%) and 4/122 (3%) in the UKR to TKR and TKR to TKR groups, respectively (p = 0.7). There was no statistical difference in the re-operation rate of either group (10% in the UKR to TKR group and 7% in the TKR to TKR group, P = 1). Stiffness was the most common indication for re-operation in the UKR to TKR group (2/61, 3%, p = 0.11) while aseptic loosening was the most common in the TKR to TKR group (4/122, 3.2%, p = 0.7). The survivorship in the UKR to TKR was 93% and 90% at 5 and 9 years, respectively. The survivorship in the TKR to TKR group was 95% and 94% at 5 and 9 years, respectively, which was not statistically different from the UKR group. Discussion. The most common reason for revision was different between the two groups (p < 0.001) while the skin to skin time was longer in the TKR to TKR group. In terms of revision components, femoral stems were never required in the UKR to TKR group while tibial stems were only required in 31%. Similarly, medial tibial augments were only required in 15% of the UKR to TKR group. While the surgeon must be prepared to use augmentation and stems in UKR to TKR revisions, they can often be completed with primary components and therefor will have an overall lower cost to the health care system. Furthermore, the survivorship and re-operation between the two groups was similar which supports previous literature. The results of this study will allow for a more in-depth cost-effectiveness analysis of UKR to TKR vs TKR to TKR in arthroplasty decision making. Unicompartmental knee replacements should be considered in appropriate patients to decrease the lifetime cost of arthroplasty intervention and potentially decrease the burden on the health care system. For figures, tables, or references, please contact authors directly


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 1 | Pages 52 - 57
1 Jan 2009
Newman J Pydisetty RV Ackroyd C

Between 1989 and 1992 we had 102 knees suitable for unicompartmental knee replacement (UKR). They were randomised to receive either a St Georg Sled UKR or a Kinematic modular total knee replacement (TKR). The early results demonstrated that the UKR group had less complications and more rapid rehabilitation than the TKR group. At five years there were an equal number of failures in the two groups but the UKR group had more excellent results and a greater range of movement. The cases were reviewed by a research nurse at 8, 10 and 12 years after operation. We report the outcome at 15 years follow-up. A total of 43 patients (45 knees) died with their prosthetic knees intact. Throughout the review period the Bristol knee scores of the UKR group have been better and at 15 years 15 (71.4%) of the surviving UKRs and 10 (52.6%) of the surviving TKRs had achieved an excellent score. The 15 years survivorship rate based on revision or failure for any reason was 24 (89.8%) for UKR and 19 (78.7%) for TKR. During the 15 years of the review four UKRs and six TKRs failed. The better early results with UKR are maintained at 15 years with no greater failure rate. The median Bristol knee score of the UKR group was 91.1 at five years and 92 at 15 years, suggesting little functional deterioration in either the prosthesis or the remainder of the joint. These results justify the increased use of UKR


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 40 - 40
7 Aug 2023
Rahman A Strickland L Pandit H Jenkinson C Murray D
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Abstract. Background. Daycase 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. Method. This 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. Results. Standard 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. Conclusion. The 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


Introduction. Unicompartmental knee replacement (UKR) offers advantages over total knee replacement but has higher revision rates particularly for aseptic loosening. Cementless UKR was introduced in an attempt to address this. We used National Joint Registry (NJR) data to compare the 10-year results of cemented and cementless mobile bearing UKR whilst matching for important patient, implant and surgical factors. We also explored the influence of caseload on outcome. Methods. We performed a retrospective observational study using NJR data on 30,814 cemented and 9,708 cementless mobile bearing UKR implanted between 2004 and 2016. Logistic regression was utilised to calculate propensity scores allowing for matching of cemented and cementless groups for various patient, implant and surgical confounders, including surgeon's caseload, using a one to one ratio. 14,814 UKRs (7407 cemented and 7407 cementless) were propensity score matched. Outcomes studied were revision, defined as removal, addition or exchange of a component, and reasons for revision. Implant survival was compared using Cox regression models and groups were stratified according to surgeon caseload. Results. Based on raw unmatched data the 10 year survival for cementless and cemented UKR were 89% (95% CI 88%–90%) and 93% (CI 90%–96%), with cementless having a lower revision rate (Hazard ratio (HR)=0.59 (CI 0.52–0.68, p<0.001). However, there were differences between the cohorts in many potential confounding factors particularly surgeons caseload: Surgeons using cementless had a higher caseloads than those using cemented and for both cohorts the revision rate decreased with increasing caseload. Following matching, all potential confounders were well balanced and the 10-year survival for cementless and cemented were 90% (CI 88%–92%) and 93% (95% CI 90–96%) with cementless having a lower revision rate (HR 0.76; CI 0.64–0.91; p=0.003). This was due to rate of revision for aseptic loosening more than halving (p<0.001) in the cementless (n=31, 0.4%) compared to cemented (n=74, 1.0%) and the rate of revision for pain decreasing (p=0.03) in the cementless (n=34, 0.5%) compared to the cemented (n=55, 0.7%). However, the rate of peri-prosthetic fracture increased significantly (p=0.01) in the cementless (n=19, 0.3%) compared to the cemented (n=7, 0.1%). Following matching the decrease in revision rate with the cementless was similar for low (<10 cases/year; HR 0.74), medium (10–30 cases/year; HR 0.79) and high (>10 cases/year; HR 0.79) caseload surgeons. The 10- year survival for cementless and cemented were for low caseload 87% & 82%, medium caseload 94% & 92% and high caseload 98% & 94% respectively. Conclusions. This is the first study to compare the 10-year survival of the cementless and cemented mobile bearing UKR. We have demonstrated that the cementless device has a 24% reduced risk of revision and that this was independent of surgeon caseload and other important patient, surgical and implant confounders. This improvement was due to the rate of revision for aseptic loosening and pain halving. However, there was a small increase in rate of periprosthetic fracture. The results of both cemented and cementless UKR improved with increasing surgeon caseload. Low volume surgeons have poor results with both cemented and cementless UKR so should consider either stopping doing UKR or doing more. Medium and high volume surgeons should consider using the cementless. High volume surgeons using the cementless had particularly good results with a 10-year survival of 98%. For figures, tables, or references, please contact authors directly


Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_11 | Pages 2 - 2
1 Oct 2019
Dodd CAF Murray DW
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Introduction. The commonest causes of revision of Unicompartmental Knee Replacement (UKR) in National Registers are loosening and pain. Cementless UKR was introduced to address loosening and was found, in small randomised studies, to have better radiographic fixation than Cemented UKR. Although non-significant these studies also suggested the clinical outcome was better with cementless. The aim of this larger study was to compare the pain and function of cementless and cemented UKR at five years. Methods. 263 Cemented and 266 Cementless UKR of identical design, implanted by four high volume surgeons for the same indications, were reviewed by independent physiotherapists at five years. Revision, re-operation, Oxford Knee Score (OKS), American Knee Society score (AKSS) and EQ-5D were assessed. Two pain specific scores were also used: Pain Detect (PD) and Intermittent and Constant Osteoarthritis Pain (ICOAP). The pain scores were normalised onto a scale of 0 to 100 with 100 being the best. The cemented cohort was mainly implanted before the cementless, although there was considerable overlap. To explore whether differences were due to progressive improvement in surgical practice with time each cohort was divided into early and late subgroups. Results. Pre-operatively there were no differences between the devices in patient demographics or scores. At 5 years there were no differences in revision rate (0.8%), re-operation rate (2.2%) or medical complication rate (4%). The Cementless had significantly (p<0.05) better OKS (43 v 41), AKSS and EQ5D. There were significantly (p=0.03) fewer cementless cases with unexplained pain (2.3% v 6%). The cementless had significantly (p<0.002), less ‘strongest’ (84 v 76) and ‘average’ (90 v 85) pain as assessed by PD and less chronic (97 v 92) and intermittent (93 v 86) pain as assessed by ICOAP. Subgroup analysis found no significant differences in outcome between the early and late subgroups within the cohorts, whereas there were significant differences in outcomes between the late subgroup of the cemented cohort and the early subgroup of the cementless cohort. Discussion and Conclusion. Almost all outcome scores were significantly better following cementless compared to cemented UKR, suggesting that the cementless is better than cemented. However, as the cemented cases were mainly implanted before the cementless, it could be the difference was due to other factors, such as surgical technique or rehabilitation, that improved with time. This is unlikely to be the case as there were no differences between the early and late subgroups within the cohorts whereas there were differences between the late subgroup of the cemented cohort and the early subgroup of the cementless cohort which were implanted at a similar time. Although the functional scores following cementless are significantly better than cemented, the differences are similar to or smaller than the minimally clinical important difference (MCID) for these scores. In contrast there is significantly less pain following the cementless and the differences tended to be greater than the MCID. This suggests that Cementless UKR is associated with appreciably less pain and slightly better function than Cemented UKR. For figures, tables, or references, please contact authors directly


The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 12 | Pages 1617 - 1620
1 Dec 2011
Willis-Owen CA Sarraf KM Martin AE Martin DK

Symptomatic and asymptomatic deep-vein thrombosis (DVT) is a common complication of knee replacement, with an incidence of up to 85% in the absence of prophylaxis. National guidelines for thromboprophylaxis in knee replacement are derived from total knee replacement (TKR) data. No guidelines exist specific to unicompartmental knee replacement (UKR). We investigated whether the type of knee arthroplasty (TKR or UKR) was related to the incidence of DVT and discuss the applicability of existing national guidelines for prophylaxis following UKR. . Data were collected prospectively on 3449 knee replacements, including procedure type, tourniquet time, surgeon, patient age, use of drains and gender. These variables were related to the incidence of symptomatic DVT. The overall DVT rate was 1.6%. The only variable that had an association with DVT was operation type, with TKR having a higher incidence than UKR (2.2% versus 0.3%, p < 0.001). These data show that the incidence of DVT after UKR is both clinically and statistically significantly lower than that after TKR. . TKR and UKR patients have different risk profiles for symptomatic DVT. The risk-benefit ratio for TKR that has been used to produce national guidelines may not be applicable to UKR. Further research is required to establish the most appropriate form of prophylaxis for UKR


The Bone & Joint Journal
Vol. 96-B, Issue 7 | Pages 928 - 935
1 Jul 2014
Matharu GS McBryde CW Robb CA Pynsent PB

The Oxford hip and knee scores (OHS and OKS) are validated patient-reported outcome measures used in patients undergoing total hip replacement (THR), hip resurfacing (HR), total knee replacement (TKR) and unicompartmental knee replacement (UKR). We analysed the absolute OHS and OKS and change in scores following THR, HR, TKR, and UKR performed at one specialist centre. All patients undergoing and completing at least one Oxford score were eligible for inclusion in the study which included 27 950 OHS and 19 750 OKS in 13 682 patients. Data were analysed using non-linear quantile regression. The median absolute Oxford scores for THR, HR, TKR and UKR were pre-operative 68.8% (15.0/48), 58.3% (20.0/48), 66.7% (16.0/48), 60.4% (19.0/48) respectively: and post-operative asymptote was 14.6% (41.0/48), 5.8% (45.2/48), 31.2% (33.0/48), 29.2% (34.0/48). The median asymptotic change from the pre-operative score for THR, HR, TKR and UKR were 47.9% (23.0/48), 47.9% (23.0/48), 33.3% (16.0/48) and 32.4% (15.5/48), respectively. The median time at which no further appreciable change in score was achieved post-operatively was 0.7 years for THR, 1.1 years for HR, 0.9 years for TKR and 1.1 years for UKR. The curves produced from this analysis could be used to educate patients, and to audit the performance of a surgeon and an institution. The time to achieve a stable improvement in outcome varied between different types of joint replacement, which may have implications for the timing of post-operative review. Cite this article: Bone Joint J 2014; 96-B:928–35


The Journal of Bone & Joint Surgery British Volume
Vol. 92-B, Issue 4 | Pages 508 - 512
1 Apr 2010
Pearse AJ Hooper GJ Rothwell A Frampton C

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


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_12 | Pages 2 - 2
1 Oct 2018
Dodd CAF Kennedy J Palan J Mellon SJ Pandit H Murray DW
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Introduction. The revision rate of unicompartmental knee replacement (UKR) in national joint registries is much higher than that of total knee replacements and that of UKR in cohort studies from multiple high-volume centres. The reasons for this are unclear but may be due to incorrect patient selection, inadequate surgical technique, and inappropriate indications for revision. Meniscal bearing UKR has well defined evidence based indications based on preoperative radiographs, the surgical technique can be assessed from post-operative radiographs and the reason for revision from pre-revision radiographs. However, for an accurate assessment aligned radiographs are required. The aim of the study was to determine why the revision rate of UKR in registries is so high by undertaking a radiographic review of revised UKR identified by the United Kingdom's (UK) National Joint Registry (NJR). Methods. A novel cross-sectional study was designed. Revised medial meniscal bearing UKR with primary operation registered with the NJR between 2006 and 2010 were identified. Participating centres from all over the country provided blinded pre-operative, post-operative, and pre-revision radiographs. Two observers reviewed the radiographs. Results. Radiographs were provided for 107 revised UKR from multiple centres. The recommended indications were not satisfied in 30%. The most common reason was the absence of bone-on-bone arthritis, and in 16 (19%) the medial joint space was normal or nearly normal. Post-operative films were mal-aligned in 50%. Significant surgical errors were seen in 50%, with most errors attributable to tibial component placement and orientation. No definite reason for revision was identified in 67%. Reasons for revision included disease progression (10%), tibial component loosening (7%), dislocation of the bearing (7%), infection (6%) femoral component loosening (3%), and peri-prosthetic fracture (2% - one femur, one tibia). Discussion and Conclusion. This study found that improper patient selection, inadequate surgical technique, inappropriate revisions and poorly taken radiographs all contributed to the high revision rate. There is a misconception that UKR should be used for early OA. Bone-on-bone arthritis is a requirement and was definitely not present in about 20%. There were many surgical errors, particularly related to the tibial cut: The new instrumentation should reduce this. There was a high prevalence of mal-aligned radiographs. Revisions should be avoided unless there is a definite problem, as the outcome of revision is usually poor in this situation. 80% of UKR revisions could potentially be avoided if surgeons adhered to the recommended indications for primary and revision surgery, and used the recommended surgical techniques. This study therefore suggests that if UKR was used appropriately the revision rate would be substantially lower and probably similar to that of TKR


The Journal of Bone & Joint Surgery British Volume
Vol. 92-B, Issue 3 | Pages 374 - 379
1 Mar 2010
Kendrick BJL Rout R Bottomley NJ Pandit H Gill HS Price AJ Dodd CAF Murray DW

With medial unicompartmental osteoarthritis (OA) there is occasionally a full-thickness ulcer of the cartilage on the medial side of the lateral femoral condyle. It is not clear whether this should be considered a contraindication to unicompartmental knee replacement (UKR). The aim of this study was to determine why these ulcers occur, and whether they compromise the outcome of UKR. Case studies of knees with medial OA suggest that cartilage lesions on the medial side of the lateral condyle are caused by impingement on the lateral tibial spine as a result of the varus deformity and tibial subluxation. Following UKR the varus and the subluxation are corrected, so that impingement is prevented and the damaged part of the lateral femoral condyle is not transmitting load. An illustrative case report is presented. Out of 769 knees with OA of the medial compartment treated with the Oxford UKR, 59 (7.7%) had partial-thickness cartilage loss and 20 (2.6%) had a full-thickness cartilage deficit on the medial side of the lateral condyle. The mean Oxford Knee Score (OKS) at the last follow-up at a mean of four years was 41.9 (13 to 48) in those with partial-thickness cartilage loss and 41.0 (20 to 48) in those with full-thickness loss. In those with normal or superficially damaged cartilage the mean was 39.5 (5 to 48) and 39.7 (8 to 48), respectively. There were no statistically significant differences between the pre-operative OKS, the final review OKS or of change in the score in the various groups. We conclude that in medial compartment OA, damage to the medial side of the lateral femoral condyle is caused by impingement on the tibial spine and should not be considered a contraindication to an Oxford UKR, even if there is extensive full-thickness ulceration of the cartilage


The Journal of Bone & Joint Surgery British Volume
Vol. 94-B, Issue 7 | Pages 919 - 927
1 Jul 2012
Baker PN Petheram T Jameson SS Avery PJ Reed MR Gregg PJ Deehan DJ

Following arthroplasty of the knee, the patient’s perception of improvement in symptoms is fundamental to the assessment of outcome. Better clinical outcome may offset the inferior survival observed for some types of implant. By examining linked National Joint Registry (NJR) and patient-reported outcome measures (PROMs) data, we aimed to compare PROMs collected at a minimum of six months post-operatively for total (TKR: n = 23 393) and unicondylar knee replacements (UKR: n = 505). Improvements in knee-specific (Oxford knee score, OKS) and generic (EuroQol, EQ-5D) scores were compared and adjusted for case-mix differences using multiple regression. Whereas the improvements in the OKS and EQ-5D were significantly greater for TKR than for UKR, once adjustments were made for case-mix differences and pre-operative score, the improvements in the two scores were not significantly different. The adjusted mean differences in the improvement of OKS and EQ-5D were 0.0 (95% confidence interval (CI) -0.9 to 0.9; p = 0.96) and 0.009 (95% CI -0.034 to 0.015; p = 0.37), respectively. We found no difference in the improvement of either knee-specific or general health outcomes between TKR and UKR in a large cohort of registry patients. With concerns about significantly higher revision rates for UKR observed in worldwide registries, we question the widespread use of an arthroplasty that does not confer a significant benefit in clinical outcome


The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 5 | Pages 622 - 628
1 May 2011
Pandit H Jenkins C Gill HS Smith G Price AJ Dodd CAF Murray DW

The contraindications for unicompartmental knee replacement (UKR) remain controversial. The views of many surgeons are based on Kozinn and Scott’s 1989 publication which stated that patients who weighed more than 82 kg, were younger than 60 years, undertook heavy labour, had exposed bone in the patellofemoral joint or chondrocalcinosis, were not ideal candidates for UKR. Our aim was to determine whether these potential contraindications should apply to patients with a mobile-bearing UKR. In order to do this the outcome of patients with these potential contraindications was compared with that of patients without the contraindications in a prospective series of 1000 UKRs. The outcome was assessed using the Oxford knee score, the American Knee Society score, the Tegner activity score, revision rate and survival. The clinical outcome of patients with each of the potential contraindications was similar to or better than those without each contraindication. Overall, 678 UKRs (68%) were performed in patients who had at least one potential contraindication and only 322 (32%) in patients deemed to be ideal. The survival at ten years was 97.0% (95% confidence interval 93.4 to 100.0) for those with potential contraindications and 93.6% (95% confidence interval 87.2 to 100.0) in the ideal patients. We conclude that the thresholds proposed by Kozinn and Scott using weight, age, activity, the state of the patellofemoral joint and chondrocalcinosis should not be considered to be contraindications for the use of the Oxford UKR


The Journal of Bone & Joint Surgery British Volume
Vol. 93-B, Issue 4 | Pages 470 - 475
1 Apr 2011
Kendrick BJL Simpson DJ Kaptein BL Valstar ER Gill HS Murray DW Price AJ

The Oxford unicompartmental knee replacement (UKR) was designed to minimise wear utilising a fully-congruent, mobile, polyethylene bearing. Wear of polyethylene is a significant cause of revision surgery in UKR in the first decade, and the incidence increases in the second decade. Our study used model-based radiostereometric analysis to measure the combined wear of the upper and lower bearing surfaces in 13 medial-compartment Oxford UKRs at a mean of 20.9 years (17.2 to 25.9) post-operatively. The mean linear penetration of the polyethylene bearing was 1.04 mm (0.307 to 2.15), with a mean annual wear rate of 0.045 mm/year (0.016 to 0.099). The annual wear rate of the phase-2 bearings (mean 0.022 mm/year) was significantly less (p = 0.01) than that of phase-1 bearings (mean 0.07 mm/year). The linear wear rate of the Oxford UKR remains very low into the third decade. We believe that phase-2 bearings had lower wear rates than phase-1 implants because of the improved bearing design and surgical technique which decreased the incidence of impingement. We conclude that the design of the Oxford UKR gives low rates of wear in the long term


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_4 | Pages 26 - 26
1 Mar 2021
Sephton B Shearman A Nathwani D
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There has been significant interest in day-case and rapid discharge pathways for unicompartmental knee replacements (UKR). Pathways to date have shown this to be a safe and feasible option; however, no studies to date have published results of rapid-discharge pathways using the NAVIO robotic system. To date there is no published experience with rapid discharge UKR patients using the NAVIO robotic system. We report an initial experience of 11 patients who have safely been discharged within 24 hours. With the primary goal of investigating factors that led to rapid discharge and a secondary goal of evaluating the safety of doing so. All patients were discharged within 24 hours; there were no post-operative complications and no readmissions to hospital. The mean length of stay was 16.9 hours (SD=7.3), with most patients seen once on average by physiotherapy. Active range of motion at 6 weeks was 0.7o to 130.5 o, with all patients mobilising independently. The average 6-month post-operative Oxford Knee Score was 43.5 out of 48. There were no readmission or complications in any of our patients. This initial feasibility study identified that patients could be safely discharged within 24 hours after UKR using the NAVIO robotic system. With growing uptake of robotic procedures, with longer operative durations than traditional procedures, it is essential to ensure a rapid discharge to reduce healthcare cost whilst ensuring that patients are discharged home in a safe manner


The Journal of Bone & Joint Surgery British Volume
Vol. 91-B, Issue 4 | Pages 469 - 474
1 Apr 2009
Gulati A Pandit H Jenkins C Chau R Dodd CAF Murray DW

Varus malalignment after total knee replacement is associated with a poor outcome. Our aim was to determine whether the same was true for medial unicompartmental knee replacement (UKR). The anatomical leg alignment was measured prospectively using a long-arm goniometer in 160 knees with an Oxford UKR. Patients were then grouped according to their mechanical leg alignment as neutral (5° to 10° of valgus), mild varus (0° to 4° of valgus) and marked varus (> 0° of varus). The groups were compared at five years in terms of absolute and change in the Oxford Knee score, American Knee Society score and the incidence of radiolucent lines. Post-operatively, 29 (18%) patients had mild varus and 13 (8%) had marked varus. The mean American Knee Society score worsened significantly (p < 0.001) with increasing varus. This difference disappeared if a three-point deduction for each degree of malalignment was removed. No other score deteriorated with increasing varus, and the frequency of occurrence of radiolucent lines was the same in each group. We therefore conclude that after Oxford UKR, about 25% of patients have varus alignment, but that this does not compromise their clinical or radiological outcome. Following UKR the deductions for malalignment in the American Knee Society score are not justified


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_13 | Pages 28 - 28
1 Nov 2015
Haddad F
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Total knee replacement (TKR) is considered the “gold standard” treatment for advanced osteoarthritis (OA) of the knee with good survivorship and functional outcomes. However up to 20% of patients undergoing TKR may have unicompartmental disease only. Treatment options for medial compartment arthritis can include both unicompartmental knee replacements (UKR) and TKR. While some surgeons favor TKR with a proven track record, others prefer UKR due to more normal joint kinematics, better proprioception and better motion. There is also a higher rate of return to sports amongst patients with UKR compared to TKR. When considering all knee procedures, partial knee replacements account for 7–9%, primary TKRs for 83–88%, and revision knee replacements for 5–8%. Unicompartmental Knee Replacements comprise more than 90% of all partial knee replacement procedures. Proponents of UKR cite as advantages the preservation of normal knee kinematics, lower peri-operative morbidity, blood loss and infection risk compared with TKRs, as well as accelerated patient rehabilitation and recovery. However, partial knee replacements have a higher rate of revision than TKRs. This may be partly because they are inserted in patients with higher expectations, and partly because they are easier to revise. As a result, the volume of UKRs implanted has diminished over time and continues to decline. We compared patient reported outcomes, satisfaction and perception of normality of the knee post-operatively between UKR and TKR. A single unit and single surgeon series of patients were recruited. Data was collated for 68 well-matched patients with more than 24 months follow-up. UKR was undertaken in patients with isolated medial compartment osteoarthritis; stable ACL and less than grade 3 lateral patellar changes of the Outerbridge classification. TKR was undertaken for the rest. The patients were assessed with validated knee scores including the Total Knee Function Questionnaire (TKFQ) which focuses on recreational and sporting outcomes as well as activities of daily living (ADL). Patient satisfaction and perception of knee normality was measured on a visual analogue scale. Thirty-four patients with a TKR and 34 patients with a UKR were analyzed. The average ages in the TKR and UKR groups were 69.25 and 67.26 years, respectively. The patients were well-matched for demographics and had equivalent pre-operative morbidities and scores. The UKR group had better WOMAC (p=0.003), SF36 (physical: p<0.001 mental: p=0.25), Oxford knee (p<0.001) and Knee Society scores (p=0.002, function: p<0.001). The UKR group showed better outcomes in the TKFQ including exercise and sport (p= 0.02), movement and lifestyle (p=0.02) and the ADL (p=0.002). There was, however, no difference in patient satisfaction scores (p=0.41) and perception of how normal the knee felt between the two groups (p=0.99). A UKR procedure confers better functional outcome in terms of recreation and sport compared to TKR procedures. While UKR is an appropriate choice in the elderly yet active patient with unicompartmental knee arthritis, satisfaction is similar to that of patients with a TKR reflecting higher pre-operative expectations. We believe that in appropriate centers, the UKR procedure is associated with excellent outcomes. UKR should have a secure place in the knee arthroplasty armamentarium provided current knowledge regarding patient selection and surgical technique is followed


Orthopaedic Proceedings
Vol. 102-B, Issue SUPP_1 | Pages 128 - 128
1 Feb 2020
Legnani C Terzaghi C Macchi V Borgo E Ventura A
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The treatment of medial knee osteoarthritis (OA) in conjunction with anterior knee laxity is an issue of debate. Current treatment options include knee joint distraction, unicompartmental knee replacement (UKR) or high tibial osteotomy with anterior cruciate ligament (ACL) reconstruction or total knee replacement. Bone-conserving options are preferred for younger and active patients with intact lateral and patello-femoral compartment. However, still limited experience exists in the field of combining medial UKR and ACL reconstruction. The aim of this study is to retrospectively evaluate the results of combined fixed-bearing UKR and ACL reconstruction, specifically with regard to patient satisfaction, activity level, and postoperative functional outcomes. The hypothesis was that this represents a safe and viable procedure leading to improved stability and functional outcome in patients affected by isolated unicompartmental OA and concomitant ACL deficiency. Fourteen patients with ACL deficiency and concomitant medial compartment symptomatic osteoarthritis were treated from 2006 to 2010. Twelve of them were followed up for an average time of 7.8 year (range 6–10 years). Assessment included Knee Osteoarthritis Outcome Score (KOOS), Oxford Knee score (OKS), American Knee Society scores (AKSS), WOMAC index of osteoarthritis, Tegner activity level, objective examination including instrumented laxity test with KT-1000 arthrometer and standard X-rays. Wilcoxon test was utilized to compare the pre-operative and follow-up status. Differences with a p value <0.05 were considered statistically significant. KOOS score, OKS, WOMAC index and the AKSS improved significantly at follow-up (p < 0.05). There was no clinical evidence of instability in any of the knees as evaluated with clinical an instrumented laxity testing (p < 0.05). No pathologic radiolucent lines were observed around the components. In one patient a total knee prosthesis was implanted due to the progression of signs of osteoarthritis in the lateral compartment 3 years after primary surgery. UKR combined with ACL reconstruction is a valid therapeutic option for young and active patients with a primary ACL injury who develop secondary OA and confirms subjective and objective clinical improvement up to 8 years after surgery


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_7 | Pages 14 - 14
1 May 2015
Smith L Wong J Cowie S Radford M Price M Langkamer V
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Unicompartmental knee replacement (UKR) is associated with higher revision rates than total knee replacement and it has been suggested that surgeons should receive specific training for this prosthesis. We investigated the outcome of all UKR in a district general hospital over ten years. All patients who had received UKR from 2003 to 2013 were identified from theatre records, as were all revision knee arthroplasties. We contacted all patients (or their GP) with no known revision to ascertain UKR status. A life table analysis was used for three categories: all surgeons and types of UKR, Oxford UKR only and Oxford UKR by surgeons with specific training. There were 319 UKR (one loss to follow up), four types of prosthesis, 21 failures and a 5-year cumulative survival rate of 91.54%. There were 310 Oxford UKR with 17 failures and 5-year survival 93.56%. Surgeons with training in use of Oxford UKR completed 242 replacements with 10 failures and 5-year survival of 95.68%. In comparison with results for Oxford UKR in 11th annual NJR report, our results are satisfactory and support continued use of this prosthesis in a non-specialist centre. Our established programme of surveillance will monitor the survival of UKR in our hospital


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_13 | Pages 46 - 46
7 Aug 2023
Rahman A Heath D Mellon S Murray D
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Abstract. Introduction. In cementless UKR, early post-operative tibial fractures are 7x more common in very small tibias. A smaller keel has been shown to reduce this fracture risk, but its effect on fixation is unassessed. This mechanical study assesses the effect of keel interference and size on sagittal micromotion of the tibial component in physiological loading positions. Method. A high-resolution Digital Image Correlation setup was developed and validated to an accuracy of 50 micrometres. Variants of tibial components were 3D-printed: standard, no-interference, no-keel, and a new small keel. Components were implanted into bone-analogue foam which was machined to a CT-reconstructed small tibia, using surgical technique. Tibias were loaded to 200N in physiological loading positions: 8mm (step-up) and 15mm (lunge) posterior to midpoint, and micromotion was assessed. Results. In all tests, anterior lift-off was the largest micromotion observed. In ‘step-up’, a standard keel moved more than the no-interference and no-keel variants (340μm-vs-63μm-vs-30μm, p=0.002). In ‘lunge’ loading, the no-interference and no-keel variants moved more than the standard (826μm-vs-1003μm-vs-521μm, p=0.039). The small keel experienced less micromotion in ‘step-up’ (245μm-vs-340μm p=0.233, overall p=0.009) and ‘lunge’ (378μm-vs-521μm p=0.265, overall p=0.006) than the standard keel. Conclusion. The keel protects against large tibial micromotion during lunge movement. Counterintuitively, interference increases micromotion during step-up movement, likely due to implant pivoting around the bone-keel interface. Results suggest patients should be advised against lunge movements early post-operatively. The new smaller keel fixes similarly or better than the standard keel, making it viable for replacing the standard keel to potentially reduce fracture risk


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_12 | Pages 32 - 32
1 Jul 2014
Dodd C
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The evidence to help the surgeon decide on the merits of which type of replacement to offer their patients is steadily mounting and comes from large datasets such as joint registries. There are many advantages of UKR vs TKR such as satisfaction, function, recovery, morbidity, mortality and cost but there is one major disadvantage. All registries show a higher failure rate with UKRs. Registries show that there are more excellent and fewer poor Patient Reported Outcome Measure Scores (PROMS) with UKR compared to TKR and the higher revision rate is in major part due to the threshold of revision. For instance, 60% of UKR are revised vs 10% of TKR with an Oxford score that is worse post-operation than pre-operation. Ease of revision with UKR is a major determinant of the higher revision rate. The real issue with UKR relates to usage. Most surgeons perform very few UKR on young patients with early arthritis viewing the procedure as a pre-TKR. Low surgeon volume equates to high revision rate in the national registries. Surgeons should either abandon UKR or do an adequate number to ensure success. Surgeons can improve their results by increasing their usage of UKR. The Unicompartmental Knee National Joint Registry (UKNJR) data shows that the optimal usage of the mobile UKR is between 20 and 50% of replacements. Fixed bearing usage is optimal at 20% but not higher. The other major advantage concerns the lower mortality rate with UKR. At 90 days it is less than half that of TKR and even at 8 years it is 10% less. For every 10 UKRs performed rather than TKR then one life is saved at 8 years. There is very little evidence suggesting that bi-UKR is necessary certainly with the mobile UKR. There is evidence, however that patellofemoral joint problems are a problem with fixed bearing UKR in the second decade


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_14 | Pages 44 - 44
1 Mar 2013
Porteous A Murray J Robinson J Hassaballa M
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Aim. To assess the survivorship of unicompartmental replacements (UKR) revised to UKR. Background: Partial revision of UKR, or revision to a further UKR is a rarely performed procedure with some data from the Australian registry suggesting that results are not good, with early revision being required. Method. All revision procedures from initial UKR are prospectively followed and scored as part of our department's knee database. We analysed the 37 cases in our database that showed revision of UKR to UKR. These included cases in the following categories: a) Mobile bearing revised to mobile bearing (n=8) b) Mobile bearing revised to fixed bearing (n=20) c) Fixed bearing revised to fixed bearing (n=9). Results. The survivorship of revisions of mobile UKR to mobile UKR was 87.5% at a mean of 5 yrs. The survivorship of revisions from mobile UKR to fixed bearing UKR was 95% at a mean of 8 yrs. The survivorship of revisions from fixed bearing UKR to fixed bearing UKR was 78% at 15 yr (1 revised at 9yrs, 1 at 12 yrs). Conclusion. Despite the perception that revision of a UKR to another UKR is likely to fail and require early revision, our results suggest that in specific circumstances acceptable survivorship and outcome are possible. MULTIPLE DISCLOSURES


Orthopaedic Proceedings
Vol. 104-B, Issue SUPP_7 | Pages 85 - 85
1 Jul 2022
Rahman A Heath D Mellon S Murray D
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Abstract. Introduction. In cementless UKR, primary fixation of the tibial component is achieved by press-fitting a keel (i.e. with interference) into a vertical slot cut into the proximal tibia. This may adversely affect the structural integrity of surrounding bone. Early post-operative peri-prosthetic tibial fractures are 7x more common in very small knees, but the aetiology of these fractures is unknown - such sizes are rarely used in the UK but more common in Asian populations. This study explores the effect of keel-related features in fracture risk of these very small tibias. Method. This in vitro study compares the effect of keel and slot depth (standard vs 33% shallower vs nil) and loading position (anterior/posterior gait range limits: mid-tibia vs 8mm posterior) on fracture load and path. 3D-printed titanium components were implanted using surgical instrumentation/technique, in bone-analogue foam machined to a CT-reconstructed very small tibia which subsequently experienced a peri-prosthetic fracture. Results. Introducing a standard slot reduces load-to-fracture by 50% (1421N-vs-710N, p<0.0001). Press-fitting a standard keel further reduces load-to-fracture by 40% (710N-vs-423N, p=0.0001). A shallower slot/keel increases load-to-fracture substantially (slot: 27% increase, 904N-vs-710N p=0.0003, slot+keel: 60% increase, 683N-vs-423N p=0.0004). Deeper keels fractured more vertically (current 8.2° vs shallow 15.5° vs nil 21°, degrees-to-vertical, p<0.0001). There was no difference caused by loading position. Conclusion. In very small tibias, a standard cementless keel significantly weakens the bone and may contribute to fractures. Therefore, decreasing interference or using a shallower keel should decrease the risk of fracture, although it might compromise fixation


Orthopaedic Proceedings
Vol. 97-B, Issue SUPP_1 | Pages 92 - 92
1 Feb 2015
Murray D
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For medial compartment disease UKR has many advantages over TKR. They give better function, faster recovery, lower morbidity and mortality but have a higher revision rate. Matched studies from the England and Wales National Joint Registry showed they are 60% more likely to achieve excellent outcomes (OKS>41) and 30% more likely to have excellent satisfaction. UKR patients were discharged 1.4 days earlier, had 35% less readmissions and 50% less major complications such as DVT/PE, infection, CVA and MI. The death rate was significantly lower: The hazard ratios being 0.2x at 30 days, 0.5x at 90 days and 0.85x at 8 years. However at 8 years the revision rate was 2x higher and the reoperation rate was 1.4x. If 100 patients receiving TKR had UKR instead, the result would be around one fewer death and three more reoperations in the first 4 years. If patients were aware of this most would select a UKR. The main reason why UKR have a high revision rate in registries is that most surgeons do small numbers and restrict their use to patients with very early disease, who often do badly. In the NJR 8% of knees are UKR and surgeons do on average 5 per year. Surgeons doing more than 20% of knees as UKR have a much lower re-operation rate which is similar to that of TKR. The Mobile bearing UKR can safely be used in up to 50% allowing many patients to have the advantages of UKR and a low re-operation rate


The Journal of Bone & Joint Surgery British Volume
Vol. 94-B, Issue 9 | Pages 1216 - 1220
1 Sep 2012
Weston-Simons JS Pandit H Jenkins C Jackson WFM Price AJ Gill HS Dodd CAF Murray DW

The Oxford unicompartmental knee replacement (UKR) is an established treatment option in the management of symptomatic end-stage medial compartmental osteoarthritis (MCOA), which works well in the young and active patient. However, previous studies have shown that it is reliable only in the presence of a functionally intact anterior cruciate ligament (ACL). This review reports the outcomes, at a mean of five years and a maximum of ten years, of 52 consecutive patients with a mean age of 51 years (36 to 57) who underwent staged or simultaneous ACL reconstruction and Oxford UKR. At the last follow-up (with one patient lost to follow-up), the mean Oxford knee score was 41 (. sd. 6.3; 17 to 48). Two patients required conversion to TKR: one for progression of lateral compartment osteoarthritis and one for infection. Implant survival at five years was 93% (95% CI 83 to 100). All but one patient reported being satisfied with the procedure. The outcome was not significantly influenced by age, gender, femoral or tibial tunnel placement, or whether the procedure was undertaken at one- or two-stages. In summary, ACL reconstruction and Oxford UKR gives good results in patients with end-stage MCOA secondary to ACL deficiency


Orthopaedic Proceedings
Vol. 98-B, Issue SUPP_2 | Pages 80 - 80
1 Jan 2016
Jenny J Diesinger Y
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Objectives. How to position a unicompartmental knee replacement (UKR) remains a matter of debate. We suggest an original technique based on the intra-operative anatomic and dynamic analysis of the operated knee by a navigation system, with a patient-specific reconstruction by the UKR. The goal of the current study was to assess the feasibility of the new technique and its potential pitfalls. Methods. 100 patients were consecutively operated on by implantation of a UKR with help of a well validated, non-image based navigation system, by one single surgeon. There were 41 men and 59 women, with a mean age of 68 years (range, 51 to 82 years). After data registration, the navigation system provided the dynamic measurement of the coronal tibio-femoral mechanical angle in full extension. The reducibility of the deformation was assessed by a manually applied torque in the valgus direction. The patient-specific analysis was based on the following hypotheses: 1) The normal medial laxity in full extension is 2° (after previous studies), 2) there was no abnormal medial laxity (which may be routinely accepted for varus knees) and 3) the total reducibility is the sum of the patient's own medial laxity and of the bone and cartilage loss. We assumed that the optimal correction may be calculated by the angle of maximal reducibility, less 2° to respect the normal medial laxity. The bone resections were performed accordingly to this calculated goal. No ligamentous balance or retension was performed. The fine tuning of the remaining laxity was performed by adapting the height of polyethylene component with a 1 mm step. The final measurements (coronal tibio-femoral angle in full extension and medial laxity in full extension) were performed with the navigation system after the final components fixation. The implantation had to fulfill these two parameters: optimal correction as defined previously, and a 2 ± 1° of medial laxity. Results. Before UKR, the mean coronal tibio-femoral angle in full extension was 3.9°± 2.4° without stress, and 0.7°+2.3° with valgus stress. The mean medial laxity in full extension before UKR was 3.2°+1.3°. After UKR, the mean coronal tibio-femoral angle in full extension was 2.6°+2.9°. The mean medial laxity in full extension after UKR was 1.9°+0.8°. The complete goal was obtained for 74% of the case. The optimal correction of the coronal tibio-femoral angle in full extension alone was achieved for 78% of the cases. 94% of the cases had an optimal medial laxity in full extension. Conclusion. The patient-specific UKR reconstruction according to the criteria defined was possible and its accuracy was good. The accuracy of a navigation system and the modularity of the prosthesis components seem to be significant prerequisites. The adaptation of the UKR to the patient may be easier, and the ligamentous physiology may be better restored because of the absence of any soft-tissue release. The final functional result may be improved