Medial unicompartmental knee arthroplasty: Correcting to neutral might be the wrong answer?
ESSKA Academy. Briggs K. 11/08/19; 285247; epEKA-53 Topic: Joint Replacement
Karen Briggs
Karen Briggs
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Introduction: Biomechanical models have demonstrated that changes in alignment dramatically increase the load in the medial compartment in varus-aligned knees.
The purpose of this study was to determine if preoperative or postoperative knee alignment was associated with mid-term outcomes following medial UKA.
Methods: Using modern surgical indications for medial UKA, a consecutive series of 143 knees in 124 patients (61 males, 63 females; mean age=65±10 years; mean body mass index 28.7±5) underwent medial UKA between 1999-2017. All patients had a physical exam and radiographic evaluation including anteroposterior and 3-foot standing alignment films. Exclusion criteria was >15º malalignment. Function was assessed using the Lysholm Score, Western Ontario and McMaster Universities Osteoarthritis Index, and Knee Injury and Osteoarthritis Outcome Score. Alignment was defined as the mechanical axis measured on 3-foot standing or anteroposterior films by an independent observer. Valgus alignment was represented by a negative number.
Results: 97 knees in 86 patients met the inclusion criteria. The mean age was 62.5±10 (50 females; 47 males). Average preoperative alignment was 6.5˚±4˚(varus) [range: -2˚(valgus) to 15˚(varus)] . Preoperative extension was .3˚±4.2˚ and flexion range of motion as 121˚±12˚. Mean postoperative followup was 8 years (range 4 to 15). Average postoperative alignment was 4.6˚±3.8˚(varus) [range: -5˚(valgus) to 14˚(varus)]. Average intraoperative alignment correction was -1.9˚(less varus). Post-operative alignment did not correlate with any outcome score postoperativley (P>0.05). When postoperative alignment was categorized into optimal (≤4°). Acceptable(5 to 7°) or large (>7°) there was no difference in any outcome scores between categories. At follow-up, mean WOMAC was 12.7±11; Lysholm was 85±18; KOOS Pain was 87±16; KOOS ADL was 90±13; KOOS QOL was 73±25. Postoperatively, extension was 1˚±2˚ and flexion was 129˚±8˚.
There were 2 failures in this cohort (2%) early in the surgeon's series. One patient had 12˚ varus corrected to 2˚ varus and revised to TKA at 19 months. The second patient was in 2˚ varus corrected to neutral. This patient was revised to TKA at 21 months.
Conclusions: Alignment was not associated with patient outcomes following medial UKA. Patients did not lose range of motion and had excellent outcomes at mean 8 years follow-up. The failure rate was low (2%).
Introduction: Biomechanical models have demonstrated that changes in alignment dramatically increase the load in the medial compartment in varus-aligned knees.
The purpose of this study was to determine if preoperative or postoperative knee alignment was associated with mid-term outcomes following medial UKA.
Methods: Using modern surgical indications for medial UKA, a consecutive series of 143 knees in 124 patients (61 males, 63 females; mean age=65±10 years; mean body mass index 28.7±5) underwent medial UKA between 1999-2017. All patients had a physical exam and radiographic evaluation including anteroposterior and 3-foot standing alignment films. Exclusion criteria was >15º malalignment. Function was assessed using the Lysholm Score, Western Ontario and McMaster Universities Osteoarthritis Index, and Knee Injury and Osteoarthritis Outcome Score. Alignment was defined as the mechanical axis measured on 3-foot standing or anteroposterior films by an independent observer. Valgus alignment was represented by a negative number.
Results: 97 knees in 86 patients met the inclusion criteria. The mean age was 62.5±10 (50 females; 47 males). Average preoperative alignment was 6.5˚±4˚(varus) [range: -2˚(valgus) to 15˚(varus)] . Preoperative extension was .3˚±4.2˚ and flexion range of motion as 121˚±12˚. Mean postoperative followup was 8 years (range 4 to 15). Average postoperative alignment was 4.6˚±3.8˚(varus) [range: -5˚(valgus) to 14˚(varus)]. Average intraoperative alignment correction was -1.9˚(less varus). Post-operative alignment did not correlate with any outcome score postoperativley (P>0.05). When postoperative alignment was categorized into optimal (≤4°). Acceptable(5 to 7°) or large (>7°) there was no difference in any outcome scores between categories. At follow-up, mean WOMAC was 12.7±11; Lysholm was 85±18; KOOS Pain was 87±16; KOOS ADL was 90±13; KOOS QOL was 73±25. Postoperatively, extension was 1˚±2˚ and flexion was 129˚±8˚.
There were 2 failures in this cohort (2%) early in the surgeon's series. One patient had 12˚ varus corrected to 2˚ varus and revised to TKA at 19 months. The second patient was in 2˚ varus corrected to neutral. This patient was revised to TKA at 21 months.
Conclusions: Alignment was not associated with patient outcomes following medial UKA. Patients did not lose range of motion and had excellent outcomes at mean 8 years follow-up. The failure rate was low (2%).
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