Clinical results and 12-year survivorship of the Physica ZUK unicompartmental knee replacement

What effect does preoperative flexion contracture have on the component angles in unicompartmental knee arthroplasty?

PURPOSE

The indication for unicompartmental knee arthroplasty (UKA) has been extended to cases with some degree of preoperative knee flexion contracture recently. The purpose of this study was to clarify the effect of flexion contracture on component angles.

MATERIALS AND METHODS

Thirty-five fixed-bearing UKAs using the spacer block technique with preoperative flexion contracture (Group FC) and 35 UKAs using the same technique without preoperative flexion contracture (Group NC) were included. Using radiographs, the coronal femoral component angle, coronal tibial component angle, sagittal femoral component angle, and sagittal tibial component angle were determined. Also, extension and flexion angles of the knee as well as coronal Hip-Knee-Ankle (HKA) angles in long-leg standing radiographs were measured. The data about the thickness of the selected insert were also collected. The above results were compared between the two groups.

RESULTS

The femoral component tended to be placed in a more varus and flexed position in Group FC, while no significant difference was found about the tibial component angles. While there was no significant difference in pre- and postoperative knee flexion angles between the two groups, flexion contracture remained postoperatively in Group FC. Preoperative HKA angle was greater in Group FC while the difference was no longer significant postoperatively. Regarding the thickness of the selected insert, thicker inserts tended to be used in Group FC.

CONCLUSIONS

In fixed-bearing UKA with the spacer block technique, the femoral component tended to be placed in a flexed and varus position in the knees with preoperative flexion contracture.

Unicompartmental knee arthroplasties: does the type of tibial component selected influence implant survival?

INTRODUCTION

Few information has been published on the survival of unicompartmental knee arthroplasty (UKA) and fixed-bearing tibial components. The aim of this study is to analyze if UKA survival varies according to UKA model used and to analyze the possible risk factors for UKA revision.

MATERIALS AND METHODS

A retrospective study analyzing 301 UKAs (ACCURIS, all-polyethylene tibial component, 152; Triathlon PKR, metal-backed tibial component, 149) was performed. Demographic parameters as well as implant survival and cause of prosthetic revision were analyzed. The Kaplan-Meier survival analysis, the log-rank test and the Cox multiple regression were used for the analysis.

RESULTS

Average follow-up was 8.1 ± 3.08-years. Average age was 68.1 ± 8.6-years; 70.4% of subjects were women. The ACCURIS UKA group had a UKA revision rate higher compared to the Triathlon PKR group (16/152, 10.6% vs 5/149, 3.4%, respectively; p < 0.001). The main cause of prosthetic revision was aseptic loosening (5/21, 23.8%). All aseptic loosening cases and tibial component collapse were reported with the ACCURIS UKA group. Overall UKA survival was 98.01% (95% CI 95.62-99.1) at 1-year, 94.27% (95% CI 90.95-96.4) at 5-years and 92.38% (95% CI 88.48-94.99) at 10-years' follow-up. There were no differences in the Kaplan-Meier survival curves regarding operated side or affected tibiofemoral compartment (log-rank test = 0.614 and 0.763, respectively). However, Kaplan-Meier survival curve according to UKA model used was different (log-rank test = 0.033). The metal-backed component appeared to be a protector factor for UKA revision when adjusted for age, sex, operated side, and affected tibiofemoral compartment (Hazard Ratio 0.32, p = 0.031).

CONCLUSION

Fixed-bearing UKAs showed excellent mid- and long-term survival rates. Aseptic loosening is the main cause of implant failure. PKR group (metal-backed component) seem to be a protector factor to UKA revision when it was compared with ACCURIS UKA group (all-polyethylene tibial component).

Long-term results of per-operative knee arthroscopy in confirming suitability for unicompartmental arthroplasty

BACKGROUND

Patient selection is key to the success of medial unicondylar knee arthroplasty (UKA). Progression of arthritis is the most common indication for revision surgery. Per-operative arthroscopy is a means of directly assessing the integrity of the lateral compartment. The aim of the study is to assess the long-term survivorship of UKA performed when per-operative arthroscopy is used as a final means of deciding whether to proceed with UKA.

METHODS

We used per-operative arthroscopy as a means to confirm suitability for UKA in a consecutive series of 279 Oxford medial UKA. Our series of UKA with per-operative arthroscopy (Group 1) was compared to all Oxford UKA (Group 2) and all UKA in the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) (Group 3).

RESULTS

The 14-year cumulative percentage revision (CPR) was 18.5% (95% CI 12.7, 26.4) for group 1, 19.7% (95% CI 18.8, 20.6) for group 2, and 19.2% (95% CI 18.5, 19.8) for group 3. There was no statistically significant difference in the (CPR) for the entire period when group 1 was compared to groups 2 or 3. Progression of arthritis was least in Group 1 compared to groups 2 and 3; 3.6 versus 4.4 and 4.1% respectively. Following per-operative arthroscopy 21.6% (77/356) of knees underwent a change of surgical plan from UKA to TKA.

CONCLUSION

In our practice, which includes per-operative arthroscopy, we have identified a reduced risk of revision due to progression of arthritis but no difference in overall long-term implant survivorship.

Survival of lateral unicompartmental knee arthroplasty at short-, mid-, and long-term follow-up: a systematic review and meta-analysis

BACKGROUND

The infrequency of lateral unicompartmental knee arthroplasty (UKA) has led to a lack of understanding of its survival. This study aimed to systematically evaluate the survivorship results of lateral UKA at different follow-ups based on available literature.

METHODS

Five databases were searched for eligible studies. Pooled survivorships with 95% confidence intervals (CIs) at 3, 5, 10, 15, and 20 years after lateral UKA were estimated using a random-effect model. Subgroup and sensitivity analyses were performed.

RESULTS

A total of 26 studies involving 5470 lateral UKAs were included. Survivorships of lateral UKA at 3-, 5-, 10-, 15-, and 20-year follow-ups were 96% (95% CI: 95-98%, I2 : 77.5%), 94% (95% CI: 93-96%, I2 : 70.8%), 88% (95% CI: 84-91%, I2 : 70.8%), 85% (95% CI: 79-91%, I2 : 70.8%), and 78% (95% CI: 71-85%, I2 : 54.2%), respectively. Subgroup analyses found that bearing type, the number of surgeons, and year of publication might be associated with implant survival outcomes.

CONCLUSION

Lateral UKA is an effective procedure with excellent survivorships at short-, mid-, and long-term follow-ups. Results suggest a single-surgeon lateral UKA using fixed-bearing. Additional well-designed studies are needed to elucidate the current findings.

Safe and reliable clinical outcomes at 2 years of a fixed-bearing partial knee arthroplasty with a morphometric tibial tray in a large worldwide population

PURPOSE

The purpose of this study was to evaluate: (1) improvement of functional and quality of life scores, (2) adverse events, (3) short-term implants survivorship of a newly designed fixed-bearing partial knee replacement (PKR) with a morphometric tibial tray in a large and multicentric population at a minimum follow-up of 2 years.

METHODS

From 2017 to 2019, 479 medial PKR were implanted by 16 non-developing surgeons from United States, Europe, and Japan. Eight patients were lost to follow-up (1.8%). Standardized follow-up procedures included patient-reported outcomes (Oxford Knee Society score, Forgotten Joint Score, EQ VAS, EQ 5D), patient satisfaction, radiographic assessments, adverse event at 2 years. Comparisons between the preoperative and postoperative values were performed using Student t test. Kaplan-Meier survivorship analysis was performed with knee revision as the endpoint.

RESULTS

The mean age was 65.6 ± 9.6 years. Mean body mass index was 29.5 ± 5.1 kg/m². Oxford Knee Society score and Forgotten Joint Score, respectively, improved from 23.7 ± 8 and 16 ± 15.8 preoperatively to 42.4 ± 6.5 and 74 ± 24.9 at 2 years (p < 0.0001). Satisfaction Score was 92.3 ± 13.4 at 2 years. Ten re-operations (2.1%) were reported including seven implant removals (1.5%). No other adverse event was reported. The causes of conversion to total knee arthroplasty were: nickel allergy (n = 2), patellofemoral osteoarthritis (n = 1), pain (n = 1), deep infection (n = 3). Two re-operations were performed due to infection, and one for internal fixation for a tibial plateau fracture. The 2-year Kaplan-Meier survival estimate was 98.4%, with implant removals as the endpoint.

CONCLUSION

This prospective multicentric study reported safe and reliable clinical outcomes of a morphometric PKR, which optimized tibial coverage and femoral fit, in a large population of patients worldwide at 2 years.

LEVEL OF EVIDENCE

Prospective cohort study-therapeutic study, Level II.

Robotic-arm assisted lateral unicompartmental knee arthroplasty: 5-Year outcomes & survivorship

INTRODUCTION

Robotic-arm assisted unicompartmental knee arthroplasty (RA-UKA) has demonstrated accurate component positioning and excellent outcomes for medial components. However, there is a paucity of literature on lateral compartment RA-UKA. The purpose of our study was to assess the midterm clinical outcomes and survivorship of lateral RA-UKA.

METHODS

This study was a retrospective review of a single-center prospectively maintained cohort of 33 patients (36 knees) indicated for lateral UKA. Perioperative, and postoperative two- and five-year Knee injury Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster Universities Osteoarthritis Score (WOMAC), and Forgotten Joint Score (FJS) patient reported outcome measures were collected. Five-year follow-up was recorded in 29 patients (32 knees).

RESULTS

Mean follow up was 5.1 ± 0.1 years. Mean age and BMI was 70.9 ± 7.2 years and 29.0 ± 4.2 kg/m2, respectively. At discharge, mean distance walked was 273.4 ± 70.4 feet, and mean pain score was 2.0 ± 2.5. At 2-year follow up, mean KOOS, WOMAC, and FJS were 75.1 ± 13.5, 15.0 ± 7.2, and 81.0 ± 23.3, respectively. At 5-year follow up, mean KOOS, WOMAC, and FJS were 75.3 ± 14.6, 14.9 ± 5.0, and 75.8 ± 27.4, respectively. Mean change in KOOS and WOMAC were 35.6 ± 27.1 and 11.7 ± 13.4 (p< .001 and p< .001). 94% of patients were very satisfied/satisfied, 3% neutral, and 3% dissatisfied. 91% met activity expectations, and 59% were more active than before. Survivorship was 100% at 5 years.

DISCUSSION

In this study, lateral RA-UKA demonstrated significantly improved clinical outcomes, high patient satisfaction, met expectations, and excellent functional recovery at midterm follow up. Comparative studies are needed to determine differences between robotic-assisted and conventional lateral UKA, as well as TKA.

Mid-term survivorship of fixed bearing unicondylar knee arthroplasty with no exclusion of early PFJ arthritis or ACL deficiency: Analysis of clinical and radiological predictors

PURPOSE

Fixed bearing (FB) UKA constituted 63.7% of unicondylar knee arthroplasties in 2020 Australian Registry with the longest UKA survivorship. The significance of patellofemoral joint (PFJ) arthritis, ACL deficiency, post-operative anteromedial pain, radiosclerosis or radiolucency on survivorship of FB UKA is not established. The aim of this study was to analyze the medium-term survivorship of fixed-bearing UKA with no exclusion of PFJ OA and ACL deficiency. Predictors for failure were analyzed.

METHODS

FB UKA performed in 2011-17 were reviewed. Cases with PFJ OA or ACL deficiency were not excluded. The effect on survivorship by ACL deficiency, PFJ arthritis, post-operative anteromedial pain and radiological abnormalities were analyzed.

RESULTS

There were 96 UKA with follow-up time of 66 ± 18 months (27-98). The mean age was 70 ± 9 years, BMI 25.8 ± 2.6 kg/m². Alignment was varus 9° ± 4° pre-operatively and varus 3° ± 3° post-operatively. There were four revisions (4.2%) and 4 deaths (4.2%). Reasons for revisions were loosening (n = 1), persistent pain (n = 2) and lateral compartment disease (n = 1). Estimated survival at 8.3 years was 94.7% (95% CI 91.6-97.7). BMI ≥30 was found to be a significant predictor for failure. The incidence of radiographic abnormalities was 75% for PFJ arthritis, 39% for tibial tray overhang, 14% for radiolucency or radiosclerosis, 5% for ACL deficiency and 5% for edge loading respectively but they were not significantly associated with lower survivorship or anteromedial knee pain. The presence of anteromedial pain after surgery in 36.5% was also not significantly associated with survivorship.

CONCLUSION

FB UKA with no exclusion of early PFJ arthritis and ACL deficiency has satisfactory medium-term survivorship. BMI ≥30 could have higher risk of all-cause revision. Tibial tray overhang, non-progressive radiolucency or radiosclerosis do not seem to be associated with anteromedial knee pain or poorer medium term survivorship.

Disease progression, aseptic loosening and bearing dislocations are the main revision indications after lateral unicompartmental knee arthroplasty: a systematic review

IMPORTANCE

Lateral unicompartmental knee arthroplasty (UKA) is a surgical option for patients with isolated lateral osteoarthritis however, the procedure has higher revision rates than medial UKA. The reason for this remains unclear; therefore, a better understanding of the indications for lateral UKA revision is needed.

AIM

The primary aim of this systematic review was to identify revision indications for lateral UKA. Secondary aims were to further investigate if revision indications were influenced by implant design and time from surgery.

EVIDENCE REVIEW

A systematic literature review was performed according to the PRISMA 2020 guidelines. Search was performed in January 2022 in MedLine, EMBASE, CINAHL and the Cochrane Library using the keywords "knee arthroplasty", "unicompartmental", "reoperation", synonyms and abbreviations. Articles published in 2000-2021 that were at least level III retrospective cohort studies with at least 10 lateral UKAs and reported all failure modes were included. Risk of bias was assessed using the ROBINS-I tool. Revision indications, patient characteristics, study design, implant types and time to failure were extracted from the selected studies. Collated data were tabulated and differences were tested using Chi-square or Fisher's exact test.

FINDINGS

A total of 29 cohort and 4 registry studies that included 7,668 UKAs met the inclusion criteria. Studies were judged as having moderate or severe risk of bias; this was associated with the retrospective nature of studies required to investigate long-term outcomes of knee arthroplasty. The main indications for lateral UKA revision were OA progression (35%), aseptic loosening (17%) and bearing dislocation (14%). The incidence of revision was similar for mobile-bearing implants (7.6%) and fixed-bearing (6.4%). For mobile-bearing implants, there was introduction of bearing dislocations as an additional mode of failure (24% cf. 0%, p < 0.001). For fixed-bearing implants, the incidence of revision was higher for all-poly-ethylene (13.9%) than metal-backed (1.8%) tibial components. Early lateral UKA failures were associated with bearing dislocations (sequential decrease from 69% under 6 months to 0% 10+ years, p < 0.001), whereas late failures were associated with OA progression (sequential increase from 0% under 6 months to 100% > 10+ years, p < 0.01). Compared with medial UKA, OA progression (41% cf. 30%, p = 0.004), malalignment (2.7% cf. 0.8%, p = 0.02), instability (4% cf. 1%, p = 0.02) and bearing dislocations (20% cf. 10%, p < 0.001) were more common for lateral UKA.

CONCLUSIONS AND RELEVANCE

OA progression, aseptic loosening and bearing dislocation were the three main revision indications for lateral UKA. Compared to medial UKA, OA progression, malalignment, instability and bearing dislocations were more common revision indications for lateral UKA. Higher survivorship of metal-backed fixed-bearing implants was found. The findings suggest that the outcomes of lateral UKA may be improved with more optimal alignment, gap balancing and patient selection.

LEVEL OF EVIDENCE

Level III systematic review.

Excellent outcomes with combined single stage Physica ZUK medial unicompartment knee replacement and anterior cruciate ligament reconstruction results in young, active patients with instability and osteoarthritis with a mean follow up of 5 years

BACKGROUND (INCLUDING THE AIM OF THE STUDY)

Young and more active patients with medial compartment osteoarthritis (OA) in conjunction with anterior cruciate ligament (ACL) deficiency are difficult to treat. The aim of this study was to explore the outcomes of combined fixed bearing Physica ZUK medial unicompartmental knee replacement (UKR) (Lima Corporate, Udine Italy) with ACL reconstruction for patients presenting with isolated medial compartment OA and symptomatic ACL deficiency.

METHODS

Patients who underwent simultaneous single stage ACL reconstruction and medial UKR between 2012 and 2020 by a single surgeon (GG) were included. Preoperative outcome measures including Lysholm, Tegner, Oxford Knee Score and VAS pain score were evaluated and were repeated postoperatively at the most recent follow up appointment.

RESULTS

Twenty four patients underwent simultaneous combined ACL and ZUK Medial UKR with a mean follow up of 5.1 years. Significant improvements in Lysholm (p < 0.001), Tegner (p < 0.001), Oxford Knee Score (p < 0.001) and VAS pain scores (p < 0.001) were seen with this combined approach with all patients returning to sport. Two patients had a minor peri-operative complication, which was treated conservatively. There were no revision procedures, and no evidence of implant loosening, however one patient had deceased due to an unrelated illness.

CONCLUSION

UKR combined with ACL reconstruction can be an effective treatment option for selected patients suffering from medial unicompartmental knee osteoarthritis and symptomatic ACL deficiency. This allowed active patients to return to sports, addressing both instability and OA pain in a specific patient population.

The effect of gender, age, BMI and Kellgren-Lawrence grade on functional outcome after Physica ZUK medial unicompartmental knee replacement

PURPOSE

Several factors influence the outcome of unicompartmental knee replacements. This study investigates the correlation of specific preoperative patient variables with postoperative functional outcomes-measured with the American Knee Society Knee (KS-KS) and Function Scores (KS-FS), as well as the difference in knee flexion pre- and postoperatively.

METHODS

In a retrospective study of 242 patients who underwent a medial Physica ZUK unicompartmental knee replacement (UKR), the American KS-KS, KS-FS as well as knee flexion were analyzed preoperatively and at 2-year follow-up. The absolute scores and improvement in scores were calculated per subgroup for gender, age, body mass index (BMI) and Kellgren-Lawrence (KL) radiological grade and compared between the subgroups.

RESULTS

All groups had a significant improvement in range of flexion, KS-KS and KS-FS. Female patients had lower preoperative scores and significantly larger improvement in knee flexion and KS-FS. Age does not seem to be associated with the postoperative functional outcome. Patients with a BMI of 30 or higher had a lower postoperative KS-KS and KS-FS as well as knee flexion. Patients with KL grade IV changes had larger gain in KS-KS compared to patients with grade III.

CONCLUSION

Overall, KS-KS, KS-FS and knee flexion improve significantly 2 years following a Physica ZUK UKR in all groups. Although excellent results were found in patients with a BMI of 30 or higher, a decrease in BMI was associated with an increase in functional outcome. KL IV grade preoperatively was associated with a better KS-KS improvement compared to the KL III group 2 years postoperatively. This information can aid surgeons in patient selection and to counsel patients on outcomes.

EVIDENCE LEVEL

III.

Potential risk of medial cortex perforation due to peg position of morphometric tibial component in unicompartmental knee arthroplasty: a computer simulation study

PURPOSE

The purpose of this study is to evaluate the risk of medial tibial cortical perforation in unicompartmental knee arthroplasty (UKA) due to peg positions on the tibial tray of the Persona Partial Knee (PPK).

METHODS

Preoperative CT images of 60 patients and 60 osteoarthritic knees (30 male and 30 female patients) were used. A tibial multiplanar reconstruction (MPR) image was reconstructed in preoperative planning software, and the implant was placed in a virtual osteotomy plane. In addition to PPK, Zimmer Unicompartmental Knee (ZUK) and TRIBRID (TBD) were used for evaluation. The horizontal distances from the medial tibial cortex to the anterior and posterior pegs (APCD/PPCD, respectively) were measured under neutral, 3-degree varus, 3-degree valgus and 2 mm distal positions. The differences between implants under the same positions and between positions using the same implants were compared. The percentage of total cases with APCD/PPCD of less than 3 mm and the perforation risk rate were calculated.

RESULTS

The APCD of PPK was significantly shorter at all positions except for the varus position of TBD. The PPCD of PPK was significantly shorter at all positions compared to ZUK and TBD. There were no cases with an APCD of less than 3 mm. Except for varus positions, the perforation risk rate of PPCD was significantly higher for PPK than the other two implants.

CONCLUSION

The posterior pegs of the PPK are located more medially than the other two implants, which may result in perforation of the medial tibial cortex during implantation. Surgeons should consider the risk involved in the type of implant used.

Comparative retrieval analysis of contemporary mobile and fixed unicompartmental knee bearing designs

There are two different concepts behind Unicompartmental Knee Replacement (UKR). Mobile bearings, as exemplified by the Oxford UKR, and fixed bearings, as exemplified by the Physica ZUK. These are the two most commonly implanted UKRs in the UK. For the first time, a comparison of the tribological features of 19 explanted Oxford and 19 explanted Physica ZUK UKRs was undertaken. Surface damage on the polyethylene (PE) inserts of the Oxford and Physica ZUK cohorts were assessed using an established semi-quantitative scoring method. The femoral components of both cohorts were assessed using a non-contact 3D profilometer to measure roughness values. It was found that the PE inserts of the Oxford cohort (22.54 ± 9.14) had statistically significant greater damage scores than the Physica ZUK cohort (16.50 ± 5.17) (p = 0.04). However, the femoral components of the Oxford cohort showed lower roughness values than the Physica ZUK cohort (p = 0.00). This is the first study that reports a comparative roughness analysis between retrieved Oxford and Physica ZUK UKR designs.

Comparable incidence of periprosthetic tibial fractures in cementless and cemented unicompartmental knee arthroplasty: a systematic review and meta-analysis

PURPOSE

(I) To determine the incidence of periprosthetic tibial fractures in cemented and cementless unicompartmental knee arthroplasty (UKA) and (II) to summarize the existing evidence on characteristics and risk factors of periprosthetic fractures in UKA.

METHODS

Pubmed, Cochrane and Embase databases were comprehensively searched. Any clinical, laboratory or case report study describing information on proportion, characteristics or risk factors of periprosthetic tibial fractures in UKA was included. Proportion meta-analysis was performed to estimate the incidence of fractures only using data from clinical studies. Information on characteristics and risk factors was evaluated and summarized.

RESULTS

A total of 81 studies were considered to be eligible for inclusion. Based on 41 clinical studies, incidences of fractures were 1.24% (95%CI 0.64-2.41) for cementless and 1.58% (95%CI 1.06-2.36) for cemented UKAs (9451 UKAs). The majority of fractures in the current literature occurred during surgery or presented within 3 months postoperatively (91 of 127; 72%) and were non-traumatic (95 of 113; 84%). Six different fracture types were observed in 21 available radiographs. Laboratory studies revealed that an excessive interference fit (press fit), excessive tibial bone resection, a sagittal cut too deep posteriorly and low bone mineral density (BMD) reduce the force required for a periprosthetic tibial fracture to occur. Clinical studies showed that periprosthetic tibial fractures were associated with increased body mass index and postoperative alignment angles, advanced age, decreased BMD, female gender, and a very overhanging medial tibial condyle.

CONCLUSION

Comparable low incidences of periprosthetic tibial fractures in cementless and cemented UKA can be achieved. However, surgeons should be aware that an excessive interference fit in cementless UKAs in combination with an impaction technique may introduce an additional risk, and could therefore be less forgiving to surgical errors and patients who are at higher risk of periprosthetic tibial fractures.

LEVEL OF EVIDENCE

V.

High survivorship rate and good clinical outcomes at mid-term follow-up for lateral UKA: a systematic literature review

PURPOSE

The purpose of this paper is to systematically review the available literature to understand the effectiveness, the survivorship, the clinical outcomes and the complications of lateral UKA.

METHODS

A review of the current literature available about lateral UKA was performed in March 2020, according to the PRISMA guidelines. Selection was based on the following inclusion criteria: (1) clinical reports of any level of evidence, (2) written in English language, (3) published from 1996 to 2020, (4) dealing with clinical data on lateral UKA. A total of 47 articles, published between 1996 and 2020, were included in the review. Quality of every article was assessed using the Modified Coleman Methodology Score.

RESULTS

A total of 47 studies were included. Mean mCMS was 45.27 (range 30-62). Mean age at surgery was 64.5 years (range 34.1-88.0 years). In 1741 patients (65.5%) a metal back implant was used and in 421 patients (15.8%) an all poly design was used. Several scores were used to evaluate clinical results (OKS, AKSS, IKS, KOOS, WOMAC, VAS). Range of motion improved with an overall mean value of 120.3° (range: 105.9°-143.3°). The mean follow-up was 60.7 months (range, 7-204 months), mean survivorship (absence of a revision) with a minimum 60 months of follow-up was 88.6% (range 74.5-100) and mean satisfaction of patients was 78.5% (range 41.0-97.9).

CONCLUSIONS

Lateral UKA seems to be an effective solution to manage lateral osteoarthritis (OA), based on preliminary results, with survivorship and satisfaction rate comparable to medial UKA and total knee arthroplasty (TKA). Nonetheless, this review highlights that the quality of studies available in current literature is low.

LEVEL OF EVIDENCE

Systematic review of level IV studies.

The effect of component alignment on clinical outcomes in fixed bearing unicompartmental knee arthroplasty

BACKGROUND

The aim of this study is to report component alignment in a series of ZUK fixed bearing unicompartmental knee arthroplasty (UKA) implants and compare this to clinical outcomes.

METHODS

The radiographs, Knee Society Scores (KSS) and knee flexion of 223 medial UKAs were evaluated. The following alignment parameters were assessed; coronal and sagittalfemoral component angle (c-FCA and s-FCA), coronal and sagittal tibia component angle (c-TCA and s-TCA)and the coronal tibiofemoralangle (c-TFA). Each alignment parameter was grouped at consecutive 2.5° intervals, mean KSS and knee flexion was then compared between the interval groups.

RESULTS

96.4% of femoral components were between 7.5° of varus and valgus and 95.1% between 7.5° extension and 5° flexion. 89.6% of tibial components were between 7.5° of varus and 2.5° valgus and 97.3% between 2.5° and 15° flexion. There was no significant difference between the KSS or knee flexion between any of the incremental groups of component alignment. Mean c-TFA was 0.2 ± 3.0°, 92.4% were between -5° (varus) and 5° (valgus). KSS were significantly greater for two of the increments with slightly more varus. Linear regression analysis showed there was very weak correlation (R² = 0.1933) between c-TFA and c-TCA.

CONCLUSIONS

The results of this study show that fixed bearing UKA components are forgiving to accommodate some variation in tibial and femoral component position without effecting clinical outcome scores or knee flexion. Limb alignment matters more than component position and knees with slight varus tibiofemoral alignment have better clinical scores than those with valgus.

Forgotten Joint Score: Comparison between total and unicondylar knee arthroplasty

BACKGROUND

The aim of this study is to assess the Forgotten Joint Score (FJS) for total knee arthroplasty (TKA) and unicondylar knee arthroplasty (UKA) with both short- and long-term follow-up.

METHODS

For a consecutive period of eight months, the FJS was sent to all patients who had undergone either a primary TKA or UKA either one, five or ten years previously at our institution. Patient demographics and operative details were recorded retrospectively. FJS were collected for three different TKA prosthesis and two different UKA prosthesis.

RESULTS

A total of 588 FJS questionnaires were completed consisting of 482 TKA and 106 UKA procedures. The mean FJS for patients with TKA and UKA were 50.2 and 65.4 respectively (p < 0.001). Mean FJS for the ZUK were statistically superior to the Oxford UKA, 73.1 versus 60.1 (p = 0.020). For TKA mean FJS were statistically better at five compared to one year follow up, 53.8 versus 44.8 (p = 0.007). For UKA the mean FJJs were greatest at 10 year follow up (69.0), but the difference between scores at one (60.4) and five (68.4) years was not statistically significant (p = 0.243).

CONCLUSION

This cross-sectional study has shown; superior FJSs for UKA compared to TKA and superior FJSs for a fixed bearing compared to a mobile bearing UKA and therefore supports the use of UKA opposed to TKA where the indications for UKA are satisfied. For TKA the FJS in the five-year post-operative group were significantly superior to those in the one-year post-operative group.

Better Implant Positioning and Clinical Outcomes With a Morphometric Unicompartmental Knee Arthroplasty. Results of a Retrospective, Matched-Controlled Study

BACKGROUND

During medial unicompartmental knee arthroplasty (UKA), tibial tray implantation requires compromise between bone coverage and rotational position. It was hypothesized that morphometric tibial tray (MTT) would improve implant positioning and subsequently clinical outcomes as compared to symmetric tibial tray (STT).

METHODS

A total of 106 patients who underwent medial UKA in our department between January 2017 and March 2018 were included matched on gender and age (53 in each group). Inclusion criteria were symptomatic medial femorotibial osteoarthritis, functional anterior cruciate ligament, primary arthritis, or osteonecrosis. Rotation of the tibial implant, tibial bone coverage, medial and posterior overhang were assessed with a postoperative computed tomography scan. The Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score Short Form (KOOS SF), and the quality of life score EuroQoL 5-Dimensions 3-Levels (EQ5D3L) were assessed at a minimum of 1-year follow-up.

RESULTS

Implants of the STT group exhibited more external rotation (6.3° ± 4.02° vs 4.6° ± 3.59°; P = .04), and medial and posterior overhang >3 mm (35% vs 0% and 22% vs 0%; P < .0001) but no difference for tibial bone coverage (97.3% ± 11.35% vs 94.7% ± 10.89%; P = .23). Global KSS (188.6 ± 6.6 vs 175.2 ± 31.7; P < .01), KOOS SF (16.9 ± 6.1 vs 22.5 ± 11.8; P < .003), and EQ5D3L (1 ± 0.1 vs 0.9 ± 0.2; P < .001) were higher in MTT group. According to the multivariate analysis, MTT had a positive independent effect on the KSS, KOOS SF, and EQ5D3L.

CONCLUSION

The use of an MTT in medial UKA allowed better implant positioning when decreasing the rate of overhang; superior short-term clinical outcomes were found as compared to STT.