Pre-Arthritic/Kinematic Alignment in Fixed-Bearing Medial Unicompartmental Knee Arthroplasty Results in Return to Activity at Mean 10-Year Follow-up

Abstract

Background: The optimal alignment strategy in unicompartmental knee arthroplasty (UKA) is debated. Recent studies have suggested that kinematic alignment may lead to improved biomechanics and outcomes. The aim of the present study was to determine if pre-arthritic/kinematic alignment of knees would result in sustained long-term restoration of function, without conversion to total knee arthroplasty (TKA), following non-robotically assisted, fixed-bearing medial UKA.Methods: A total of 236 UKAs were performed from 2000 to 2015. Of these, a total of 150 medial UKAs met the inclusion criteria and were included in the study. There were 76 UKAs performed in female patients. The mean age was 65 ± 10 years and the mean body mass index was 28.6 ± 5 kg/m 2 . Patients with ‡15°of varus alignment preoperatively were excluded. Varus deformity was evaluated with use of the hip-knee-ankle angle (HKAA). Pre-arthritic/kinematic alignment was estimated with use of an arithmetic HKAA (aHKA, calculated as the medial proximal tibial angle minus the lateral distal femoral angle). We defined pre-arthritic/kinematic alignment as a postoperative HKAA within 3°of the aHKA. The primary outcome measures were the Knee Injury and Osteoarthritis Outcome Score (KOOS) Activities of Daily Living and Sport subscales, including the percentage of patients who met the patient acceptable symptom state (PASS) for these measures. Failure was defined as conversion to TKA. Results:The mean follow-up was 10 years (range, 4 to 20 years), with a mean survival time estimate of 18.3 years (95% confidence interval [CI], 17.8 to 18.8). The rate of conversion to TKA was 3% (5 of 150 UKAs). Postoperatively, 127 (85%) of 150 knees were pre-arthritic/kinematically aligned, and 23 knees (15%) were not. Patients with compared to those without pre-arthritic/kinematically aligned knees had significantly longer mean survival (18.6 years; 95% CI, 18.2 to 19) compared with 15.4 years; 95% CI, 13.4 to 17.5, respectively; p = 0.008) and higher KOOS Activities of Daily Living (92 compared with 74; p < 0.001) and Sport subscale scores (74 compared with 36; p < 0.001). A greater proportion of knees in the pre-arthritic/kinematically aligned cohort met the PASS for the KOOS Activities of Daily Living (85%, 106 of 125 knees) and Sport subscales (109 of 125, 87%) compared with the non-pre-arthritic/kinematically aligned cohort (28% and 57%, respectively; p < 0.01).Conclusions: Pre-arthritic/kinematically aligned knees in this non-robotically assisted fixed-bearing medial UKA cohort had superior outcomes, including the KOOS Activities of Daily Living and Sport subscales and achievement of the PASS for these measures, compared with non-pre-arthritic/kinematically aligned at an average of 10 years after UKA. Knees that fell within 3°of a simple aHKA measurement on a 3-foot (1-m)-long standing radiograph had greater longevity and return to activities.Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence. Optimal alignmen...

Return to Sport in Middle-aged and Older Athletes After Unicompartmental Knee Arthroplasty at a Mean 10-Year Follow-up: Radiographic and Clinical Outcomes

“…[11][12][13][14][15][16]28,39 Survivorship after UKA is .18 years, with survival rates .90% at 10 years. [31][32][33][34]36 This is in comparison with recent reports of 87% survivorship at 10 years for osteotomy 5 and a 14% revision rate for cartilage procedures. 38 Return to activities has been reported to be as high as 90% at 10 years after lateral UKA and .95% at 8 years after medial UKA without increased risk of revision.…”

“…Hip-knee-ankle angle was calculated to determine the mechanical alignment. 34 All radiographic measurements were completed by an independent research examiner (K.K.B. ).…”

“…38 Return to activities has been reported to be as high as 90% at 10 years after lateral UKA and .95% at 8 years after medial UKA without increased risk of revision. [31][32][33][34]36 While previous studies have reported return to sport after UKA, 4,15,23,30,42 information on the type of sport (moderate vs vigorous), timing, and specific sports is lacking in the literature.…”

The Lawrence D. Dorr Surgical Techniques & Technologies Award: Patient Acceptable Symptom State (PASS) in Medial and Lateral Unicompartmental Knee Arthroplasty: Does the Status of the ACL Impact Outcomes?

“…Preoperative and postoperative physical examination included knee range of motion measurements, ligamentous examination, and assessment of varus or valgus deformity. Standard radiographic evaluation was performed preoperatively and postoperatively that included anteroposterior, Rosenberg [17], Merchant [18], and Hughston views [19], as well as a 3-foot (full limb) long-standing radiograph [20,21] used to assess limb alignment and the status of the joint line and prosthesis.…”

Restoration or relative overcorrection of pre-arthritic coronal alignment leads to improved results following medial unicompartmental knee arthroplasty

“…In contrast, individualized alignment strategies aim to recreate a patient’s pre‐arthritic alignment (i.e., prior to the onset of OA), often guided by re‐tensioning of the medial collateral ligament (MCL). A recent study of 150 medial UKAs reported better long‐term functional outcomes and implant survivorship of knees that were restored to their pre‐arthritic alignment compared to knees that were not [25]. Similarly, individualized strategies in TKA also referred to as kinematic alignment, have been shown to yield improved postoperative clinical outcomes compared to mechanically aligned knees [19].…”