Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-3367-9


No difference in anterior knee pain after medial unicompartmental knee arthroplasty in patients with  or without patellofemoral osteoarthritis Eun-Kyoo Song · Ju-Kwon Park · Chan-Hee Park · Min-Cheol Kim · Pranav R. Agrawal · Jong Keun Seon 

Received: 14 October 2013 / Accepted: 26 September 2014 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2014

Abstract  Purpose  The purpose of the present study was to compare functional outcomes of medial unicompartmental knee arthroplasty (UKA) in patients with patellofemoral osteoarthritis (PF OA) and those without PF OA and to evaluate the effect of PF OA on functional outcomes after UKA. Methods  The outcomes of 48 knees in patients without PF OA who underwent medial UKA (non-PF OA group) were compared to the outcomes of 57 knees in patients with PF OA [Kellgren–Lawrence (K–L) grade ≤2] who underwent medial UKA (PF OA group) with a median follow-up of 5.4 years (range 3.1–10.2 years). Clinical outcomes including anterior knee pain, HSS scores, radiological parameters, and the progression of patellofemoral osteoarthritis were compared, and their effects on functional outcomes were evaluated at the final follow-up visits. Results  At final follow-up visits, no significant intergroup difference was found in terms of anterior knee pain (1.9 vs. 1.9 in non-PF OA and PF OA groups, respectively), HSS score, or range of motion. Preoperative anterior knee pain and patellofemoral joint degeneration were found to be unrelated to poor outcome in patients that underwent medial UKA. Furthermore, no correlation was found between any functional outcome variable and chondral lesion pattern. Conclusions  The result of UKA for medial unicompartmental knee osteoarthritis was excellent regardless of PF OA (K–L grade ≤2). Hence, the patients with medial unicompartmental OA combined with a moderate degree

E.-K. Song · J.-K. Park · C.-H. Park · M.-C. Kim · P. R. Agrawal · J. K. Seon (*)  Center for Joint Disease, Chonnam National University Hwasun Hospital, Hwasun, Jeonnam, South Korea e-mail: [email protected]; [email protected]

of anterior knee pain or patellofemoral arthritis should be viewed as appropriate candidates for medial UKA. Level of evidence III. Keywords  Unicondylar knee arthroplasty · Patellofemoral osteoarthritis · Clinical outcomes · Radiological outcomes

Introduction Unicompartmental knee arthroplasty (UKA), considered as good treatment options for elderly patients with isolated medial compartment of the knee, provides more natural knee kinematics than total knee arthroplasty [3, 7, 13, 21]. The presences of radiographic findings or clinical symptoms of patellofemoral osteoarthritis are often considered as contraindications to medial UKA. In addition, several previous studies have reported that progression of osteoarthritis in the patellofemoral compartment is the most common reason for UKA failure which requires conversion to TKA [1, 8, 9, 12]. On the other hand, some authors have reported that the state of the patellofemoral joint does not affect outcome. Therefore, the state of patellofemoral joint has been recommended to be ignored when deciding UKA [4–6, 11], especially mobile-bearing UKA. Most studies evaluated the effect of patellofemoral osteoarthritis on UKA outcomes in mobile-bearing prosthesis. Few studies evaluated the effect of cartilage lesion location in patellofemoral joint on clinical outcomes. Accordingly, further study on the relation between patellofemoral joint condition and outcome is required. Therefore, the objective of this study was to compare the outcome of fixed-bearing UKA in patients with patellofemoral osteoarthritis (PF OA group) and those without


Knee Surg Sports Traumatol Arthrosc

PF OA (non-PF OA groups) and to evaluate the effects of chondral lesion grade and location on functional outcomes in the PF OA group. Our hypothesis was that the functional outcomes in patients after fixed-bearing UKA may be influenced by the preoperative patellofemoral osteoarthritis of Kellgren–Lawrence (K–L) grade ≤2. Materials and methods A total of 105 consecutive medial UKA were performed between January 2003 and October 2008. The study cohort consisted of 3 men and 96 women with median age of 64 years (range 43–81 years). UKA was indicated for patients who experienced difficulties performing daily activities due to severe pain caused by medial compartmental osteoarthritis and with less than 15° of varus deformity which could be readily corrected during valgus stress tests. Preoperative assessments revealed that all 105 knees had flexion contracture within 15° and could flex to more than 90°. Age and weight did not influence patient selection (Table 1). Prior open knee surgery, the presence of inflammatory osteoarthritis, and a non-intact anterior cruciate ligament based on Lachman’s test and MRI findings were considered as the contraindications. However, the presence of anterior knee pain (visual analogue scale/VAS ≤5) and radiological evidence of degenerative osteoarthritis on the patellofemoral joint (K–L grad [14] ≤2 by Merchant’s radiography) were not considered contraindications. Patients were divided

into two groups based on the presence of patellofemoral osteoarthritis (PF OA), according to K–L grading system on Merchant’s radiograph. The non-PF OA group consisted of 48 knees without PF OA (K–L grade 0). The PF OA group consisted of 57 knees with intra-operative evidence of PF OA (K–L grade 1 and 2) with a median follow-up of 5.4 years (range 3.1–10.2 years). All operations were performed in a standard fashion by a single surgeon under epidural or general anaesthesia through a medial parapatellar skin incision. The tibial cut was performed using extramedullary instrumentation. Intramedullary instrumentation was used for the distal femoral cutting. All arthroplasties were performed using Miller–Galante (Zimmer, Warsaw, Indiana, USA) fixed-bearing unicompartmental knee prostheses that were cemented. Active and passive range of motion (ROM) exercises were started on the first postoperative day and progressed if tolerated. All patients were allowed weight bearing when patients were tolerable to pain. Clinical evaluations were performed preoperatively and at postoperative 3 years. Clinical results included the followings: (1) anterior knee pain VAS scores during stair climbing, (2) Hospital for Special Surgery (HSS) scores (pain, function, ROM, muscle strength, flexion deformity, and instability), and (3) ranges of motion (ROMs). Radiological indices including mechanical axes on standing entire leg anteroposterior radiographs and osteoarthritic progression on the patellofemoral joint in Mechant’s view at final follow-up were determined using K–L staging system.

Table 1  Preoperative demographics of patients and comparison of clinical measurement at the time of preoperative and final follow-up Non-PF OA group (n = 48)

PF OA group (n = 57)



Preoperative values  Sex (M/F) 1/47  Mean age (years) 65.0 −6.9  Mean mechanical axis (angle)a  Median follow-up (years) 5.6  Mena body mass index (BMI) 22.48 Preoperative clinical measurement  Median anterior knee pain checked with VAS score 2.0  Mean HSS score 58.9  Median ROM 130 Final follow-up clinical measurement (postoperative 3 years)  Median anterior knee pain checked with VAS score 1.9  Mean HSS score 94.7  Median ROM


SD 6.7 SD 2.5 Range 3.1–10.0 SD 1.16

2/55 63.5 −6.3 5.4 23.01

65.0 −6.9 Range 3.1–10.2 SD 1.30

n.s n.s. n.s. n.s. n.s.

Range 1.2 SD 11.3 Range 100–140

4.0 58.1 133.0

1.5 SD 12.2 Range 110–140

0.001 n.s. n.s.

Range 0–4 SD 5.9

1.9 95.2

Range 0–4 SD 4.7

n.s. n.s.

Range 110–140


Range 100–140


PF OA patellofemoral osteoarthritis, HSS Hospital for Special Surgery scores, ROM range of motion a

  Negative values indicate varus alignment


p value

Knee Surg Sports Traumatol Arthrosc

To evaluate patellar chondral lesions during operations, the International Cartilage Repair Society (ICRS) classification was used [10, 15], which was based on the chondral defect severity: grade 0 = no cartilage lesion, grade 1 = a normal contour with superficial lesions, fissures, cracks, and indentations, grade 2 = involvement of 50 % of entire cartilage thickness, and grade 4 = full-thickness cartilage loss. To classify cartilage lesion locations, patellofemoral joints were divided into the following three compartments: the medial patellar facet, the lateral patellar facet, and the trochlea. To evaluate their effects on clinical outcomes, VAS scores, HSS scores, and ROMs were evaluated by an observer who is blind to patients’ group. To ensure reproducibility of radiographic parameters, two investigators who were unaware of surgical techniques or clinical outcomes carried out measurements twice on each patient on different days. This prospective cohort study was approved by Chonnam National University Hwasun Hospital Institutional Review Board (2012–2029), and informed consent was obtained from all patients (Fig. 1). Statistical analysis A priori power analysis was performed using the number of VAS score after UKA as the primary outcome variable. The sample size was calculated based on the data obtained from the 15 cases in the non-PF OA group and 15 cases in the PF OA group. Data showed that the VAS anterior knee pain score was 1.9 in the non-PF OA group and 2.4 in the

PF OA group with a standard deviation (SD) of 1.2 points. Based on these results, we found that 46 patients per group were required to examine the VAS anterior knee pain score (power 0.8; confidence level 0.05). The assumption of the normality of numerical data was checked by using Shapiro– Wilk’s test. The independent sample t test or Mann–Whitney’ test was used to compare the two groups in terms of numerical demographic characteristics, preoperative and postoperative measurements, and surgical data depending on whether the data were normally distributed. Paired t test was used to analyse intra-group differences before and after surgery. The chi-square on categorical data test was used to determine the differences in the progression of osteoarthritis after surgery between the two groups. To evaluate the effect of grade of ICRS or location of cartilage lesion on clinical outcomes at follow-up, multivariable linear regression analysis was carried out with anterior knee pain, HSS, and ROM each as a dependent variable, whereas preoperative anterior knee pain was used as a covariate. Inter-rater and intra-rater agreements for all measurements in radiographs were calculated using the intra-class correlation coefficient. Statistical analysis was performed using SPSS for Windows (Release 11.0; SPSS Inc, Chicago, Illinois, USA). Statistical significance was considered when p value was

No difference in anterior knee pain after medial unicompartmental knee arthroplasty in patients with or without patellofemoral osteoarthritis.

The purpose of the present study was to compare functional outcomes of medial unicompartmental knee arthroplasty (UKA) in patients with patellofemoral...
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