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.

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.

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.

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

BACKGROUND: The Physica ZUK is a fixed bearing unicompartmental knee replacement. The purpose of this prospective cohort study was to determine the mid-term clinical outcomes and survivorship of the Physica ZUK. METHODS: From 2005 to 2017 a total of 466 Physica ZUK prostheses were implanted in 398 patients by a single surgeon. The series consisted of 452 medial and 14 lateral unicompartmental knee arthroplasties (UKAs). Three hundred and sixty-seven medial UKAs with a minimum follow-up of two years (median 5.4 years) and 14 lateral UKAs with a minimum follow-up of 18 months (median 5.3 years) were analysed using the Knee Society Knee Score (KS-KS) and Function Score (KS-FS) at latest follow-up. Kaplan Meier survivorship analysis was performed with implant revision as the end point. RESULTS: Mean age at the time of surgery was 67 (range 42-88) and 58 (47-69) years for patients undergoing medial and lateral UKA respectively. For medial UKAs the KS-KS and KS-FS improved significantly compared to the pre-operative values from 53.6 and 54.0 to 93.4 and 91.0 respectively (p = 0.0001). For lateral UKAs the KS-KS and KS-FS improved significantly from 46.4 and 48.7 to 91.3 and 93.1 respectively (p = 0.0001). Six cases of medial UKA were revised to total knee arthroplasty. Medial implant survivorship was 97.9% (95% confidence intervals, 95.6-99.0%) at both five and 10 years. No lateral implants were revised. CONCLUSION: This prospective cohort study shows encouraging short to mid-term clinical results and survivorship for the Physica ZUK unicompartmental knee replacement.

Tibial Component In Total Knee Replacement :The Effect Of Overhang And Sizing On Outcome.

The aim of this study was to find a relationship between tibial overhang, malpositioning and oversizing, and the functional outcome. 188 patients were included in this retrospective study. All patients completed an Oxford knee score questionnaire at mean followup of 5 years. Anteroposterior radiographs of the total knee replacements were reviewed for medial and lateral overhang and oversizing. Lateral overhang was seen in 32.9% of patients with a mean Oxford knee score of 24.7. However lateral overhang proved no significant correlation with the functional outcome. Oversizing was seen in 31.9% of patients and, with a mean of 25.6, oversizing did have a correlation with Oxford Knee score. This study confirms that neither medial or lateral overhang of the tibial component influences functional outcome, independent of the severity of overhang. Oversizing the tibial component however, does show worse functional outcome scores at a 5 year review.

Effect of femoro-tibial component size mismatch on outcome in primary total knee replacement.

BACKGROUND: Most total knee arthroplasty systems allow a degree of femoro-tibial component size mismatch. We aim to investigate the influence of size mismatch on outcome after primary total knee arthroplasty. METHODS: We reviewed 332 patients with cruciate-retaining Genesis II total knee arthroplasty with regard to femoro-tibial component size mismatch and Oxford Knee Score (OKS). We evaluated effects of Body Mass Index, gender and patellar procedure. Minimum follow-up is five years. We divided patients into four groups (tibial component larger than femoral component, no mismatch, femoral component one size larger and femoral component two sizes larger than tibial component). RESULTS: There was no statistically significant difference in OKS between the four groups. Size mismatch did not have a statistical significant effect on OKS in a multivariate analysis. Women had mismatched components in 66% of all cases and men in 40% of all cases. CONCLUSIONS: Our study showed no statistically significant effect of femoro-tibial size mismatch on outcome after total knee replacement. Compared to men, women tend to have more component size mismatch. LEVEL OF EVIDENCE: Level III, retrospective comparative study.