Fixed Flexion Deformity After Unicompartmental Knee Arthroplasty: How Much Is Too Much

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.

Preoperative Flexion Contracture Does Not Compromise the Outcomes and Survivorship of Medial Fixed Bearing Unicompartmental Knee Arthroplasty

BACKGROUND

Despite the expanding indications for unicompartmental knee arthroplasty (UKA), the classic indication that limits flexion contracture to <5° in fixed bearing UKA excludes most patients with arthritic knees and has not been challenged in modern literature. This study compared the clinical outcomes between patients with severe flexion contracture and controls undergoing UKA.

METHODS

Eighty seven medial fixed bearing UKAs performed in patients with severe (≥15°) flexion contracture were matched 1:1 with 87 controls without flexion or recurvatum deformity (-5°<extension<5°) using propensity scores to control for age, sex, BMI, Charlson comorbidity index, ASA class, and baseline patient-reported outcome measures (PROMs). Perioperative outcomes were recorded. Range of motion, Knee Society Score, Oxford Knee Score, SF-36, and patient satisfaction were assessed at 6 months and 2 years. Survivorship was recorded at mean 11.5 ± 3.2 years.

RESULTS

Preoperative knee extension in the control and contracture groups was 0.9° ± 1.9° and 18.0° ± 3.5° (P < .001), respectively, whereas flexion was 122.8° ± 27.9° and 120.6° ± 13.6° (P = .502). The contracture group had poorer Knee Society functional (P = .023) and SF-36 physical score (P = .010) at 6 months. However, there was no difference in PROMs at 2 years. A similar proportion achieved the minimal clinically important difference for each PROM and was satisfied with surgery. Range of motion remained poorer in the contracture group and a higher percentage had residual contractures (P < .001). Ten-year survivorship was 94% and 97% in the control and contracture groups, respectively (P = .145).

CONCLUSION

Although patients with severe flexion contractures had a poorer range of motion and postoperatively, these patients attained comparable PROMs, satisfaction rates, and mid-term survivorship after UKA.

LEVEL OF EVIDENCE

III, therapeutic study.

Functional outcome and quality of life in patients with hip fracture after total knee arthroplasty

INTRODUCTION

Hip fractures are a cause of significant morbidity. While rare, ipsilateral hip fractures within 12 months after total knee arthroplasty (TKA) can negatively affect the functional outcome and the quality of life for patients who have had TKA. This aim of this study is to investigate (1) the incidence of hip fracture within 12 months after TKA and (2) the influence of hip fracture after TKA on functional outcome and quality of life in patients.

METHODS

Between March 1999 and February 2012, 25 patients who sustained an ipsilateral hip fracture within 12 months after TKA were included in this study. A propensity score matching algorithm was used to select a 1:3 control group without hip fracture. All patients were assessed using the Oxford Knee Score (OKS), Knee Society Function Score (KSFS), Knee Society Knee Score (KSKS), Physical Component Score (PCS) and Mental Component Score (MCS) of SF-36®.

RESULTS

The incidence of hip fracture was 0.16% among male patients and 0.20% for female patients. At 24 months after TKA, the OKS was 36 ± 7 in the hip fracture group versus 41 ± 5 in the control group (p = 0.003). The KSFS was 50 ± 24 in the hip fracture group versus 68 ± 21 in the control group (p = 0.001), while the KSKS was 83 ± 12 and 87 ± 8, respectively (p = 0.166). The PCS was 37 ± 12 in the hip fracture group versus 47 ± 11 in the control group (p < 0.001), while the MCS was 55 ± 10 and 54 ± 11, respectively (p = 0.664).

CONCLUSION

Although hip fracture during the rehabilitation period after TKA is uncommon, these patients have poorer functional outcome and quality of life. We recommend additional caution against hip fracture after TKA.

Unicompartmental knee arthroplasty: Current indications, technical issues and results

An age younger than 60 years, a body weight of 180 lb (82 kg) or more, performing heavy work, having chondrocalcinosis and having exposed bone in the patellofemoral (PF) joint are not contraindications for unicompartmental knee arthroplasty (UKA).Severe wear of the lateral facet of the PF joint with bone loss and grooving is a contraindication for UKA.Medial UKA should only be performed in cases of severe osteoarthritis (OA) as shown in pre-operative X-rays, with medial bone-on-bone contact and a medial/lateral ratio of < 20%.The post-operative results of UKA are generally good. Medium-term and long-term studies have reported acceptable results at 10 years, with implant survival greater than 95% for UKAs performed for medial OA or osteonecrosis and for lateral UKA, especially when fixed-bearing implants are used.When all implant-related re-operations are considered, the 10-year survival rate is 94%, and the 15-year survival rate is 91%.Aseptic loosening is the principal failure mechanism in the first few years in mobile-bearing implants, whereas OA progression causes most failures in later years in fixed-bearing implants.The overall complication rate and the comprehensive re-operation rate are comparable in both mobile bearings and fixed bearings.The survival likelihood of the all-polyethylene UKA implant is similar to that of metal-backed modular designs for UKA.Notable cost savings of approximately 50% can be achieved with an outpatient UKA surgery protocol. Outpatient surgery for UKA is efficacious and safe, with satisfactory clinical results thus far. Cite this article: EFORT Open Rev 2018;3:363-373. DOI: 10.1302/2058-5241.3.170048.

Postoperative fixed flexion deformity greater than 10° lead to poorer functional outcome 10 years after unicompartmental knee arthroplasty

PURPOSE

The primary aim of this study was to evaluate the influence of postoperative fixed flexion deformity (FFD) on the clinical outcomes 10 years after unicompartmental knee arthroplasty (UKA). The secondary aim was to identify predictors for the occurrence of postoperative FFD.

METHODS

Patients who underwent UKA between 2003 and 2007 were prospectively followed up for 10 years. A total of 172 patients were categorized into 3 groups based on the amount of postoperative FFD: (1) 0° or less (Min-FFD), (2) 1°-9° (Mid-FFD), and (3) 10° or more (Max-FFD). Functional outcome was quantified using Knee Society Function Score (KSFS), Knee Society Knee Score (KSKS) and Oxford Knee Score (OKS).

RESULTS

At 10 years after UKA, the mean KSKS and OKS were 6 ± 5 (95% CI 6-18, p = 0.050) and 5 ± 2 (95% CI 0-9, p = 0.041) points lower in patients with Max-FFD than those with Min-FFD. Other clinical outcomes were not different between groups. Patients with a higher preoperative body mass index (OR 1.122 per unit increase, 95% CI 1.006-1.253, p = 0.040) or worse preoperative FFD (OR 1.108 per unit increase, 95% CI 1.022-1.201, p = 0.013) were at increased risk of having postoperative FFD of 10° or more at 10 years after UKA.

CONCLUSIONS

The clinical relevance of this study was to demonstrate the long-term negative correlation between severe postoperative FFD and functional outcome and, therefore, the importance of achieving good knee alignment after UKA. The authors recommend that FFD should be fully corrected intra-operatively if possible while preserving knee balance and stable dynamic function through full range of motion.

LEVEL OF EVIDENCE

Prognostic level II.

Elimination of Preoperative Flexion Contracture as a Contraindication for Unicompartmental Knee Arthroplasty

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) is an effective alternative to total knee arthroplasty (TKA) for the management of unicondylar osteoarthritis. Historical contraindications limit patients' eligibility for UKA. However, recent reports have suggested that some contraindications may not be absolute. This study evaluates preoperative flexion contracture with regard to UKA.

METHODS

This study was a retrospective review of 53 patients with preoperative flexion contracture between 11° and 20° who underwent fixed-bearing UKA and a matched cohort of 53 patients who underwent cruciate-retaining TKA.

RESULTS

Preoperatively, the average flexion contracture was 13.8° in the UKA group and 14.1° in the TKA group (P = 0.42). Mean preoperative motion was greater in the patients treated with UKA (106°) than in those treated with TKA (97°; P < 0.001). Postoperatively, patients who underwent UKA had greater motion than patients who underwent TKA had (121° versus 113°; P < 0.01). Residual flexion contracture was greater in the UKA group (4.1°) than in the TKA group (2.1°; P = 0.02). The two groups demonstrated similar improvements in Knee Society clinical scores (P = 0.32). However, patients treated with UKA demonstrated higher Knee Society functional scores, compared with patients treated with TKA (86 versus 75; P = 0.03).

DISCUSSION

Although residual flexion contracture was worse after UKA, this group had similar clinical improvement, greater postoperative motion, and greater function scores, compared with the matched TKA group. Preoperative flexion contracture >5° may not be an absolute contraindication to UKA.

CONCLUSION

The contraindications to UKA regarding flexion contracture may not be as absolute as previously thought. Larger, prospective studies are needed to generalize these findings to a wider population.

Does obesity influence early outcome of fixed-bearing unicompartmental knee arthroplasty?

Obesity is a known major contributing risk factor for knee osteoarthritis (OA). It is also believed that obese unicompartmental knee arthroplasty (UKA) patients tend to have poorer outcome and possible early failure. The purpose of this study is to investigate the early outcome of obese UKA patients in a single institution. Patients who underwent fixed bearing medial UKA in between year 2005 and 2010 were included in this study. They were divided into four groups based on Body Mass Index (BMI): 25 kg/m² (Control); 25-29.9 kg/m² (Overweight); 30-34.9 kg/m² (Obese); >35 kg/m² (Severely Obese). Functional outcome was assessed using Knee Society Score (KSS), Oxford Knee Score (OKS) and Short-form 36 (SF-36). One-way ANOVA with Bonferroni post-hoc test was used to compare the four groups for quantitative variables. There were 673 patients in this study, no significant difference between the four BMI groups for gender and side of operated knee ( p > 0.05). The functional outcome of all four groups at 2 years were comparable (all p > 0.05). At a mean follow up of 5.4 (range 2.5, 8.5) years, 9 revision surgeries (1.3%) were identified. The mean duration from initial surgery to revision surgery was 49 months (Range 6, 90). Patients' pre-operative BMI did not influence the early outcome of UKA patients. However, patients with higher BMI had relatively lower functional score prior to the surgery and tended to be younger. This did not translate to early failure and the functional improvement was similar among all four groups.