Tomoharu Mochizuki1, Osamu Tanifuji2, Takashi Sato3, Hiroki Hijikata2, Hiroshi Koga2, Satoshi Watanabe3, Yukimasa Higano4, Akihiro Ariumi5, Takayuki Murayama6, Hiroshi Yamagiwa7, Naoto Endo2. 1. Department of Orthopedic Surgery, Department of Regenerative and Transplant Medicine, Graduate School of Medical and Dental Science, Niigata University, 1-757 Asahimachi-dori Chuo-ku, Niigata City, Niigata, 951-8510, Japan. tommochi121710@gmail.com. 2. Department of Orthopedic Surgery, Department of Regenerative and Transplant Medicine, Graduate School of Medical and Dental Science, Niigata University, 1-757 Asahimachi-dori Chuo-ku, Niigata City, Niigata, 951-8510, Japan. 3. Department of Orthopaedic Surgery, Niigata Medical Center, Niigata, Japan. 4. Department of Orthopaedic Surgery, Tsuruoka Municipal Shonai Hospital, Niigata, Japan. 5. Department of Orthopaedic Surgery, Nagaoka Chuo General Hospital, Niigata, Japan. 6. Department of Orthopaedic Surgery, Niigata Prefectural Central Hospital, Niigata, Japan. 7. Department of Orthopaedic Surgery, Saiseikai Niigata Daini Hospital, Niigata, Japan.
Abstract
PURPOSE: Flexion instability following total knee arthroplasty (TKA) is a common indication of early revision. The association between the objective anteroposterior (AP) laxity direction in mid-range flexion and the subjective healing of instability remains unclear; thus, this study aimed to clarify this association. METHODS: In this study, 110 knees (74 females, 92 knees; 16 males, 18 knees) with medial pivot implants were examined with a median age of 79 (range 60-92) years for a median follow-up duration of 22 (range 6-125) months. AP laxity was measured using a KT-1000 arthrometer. Self-reported knee instability score was used for the subjective healing of instability. RESULTS: Eighty-seven knees did not feel unstable (Group 0), whereas 23 knees felt unstable (Group 1). There was a significant difference in AP displacement [Group 0: median 6 mm; range 2-15 mm and Group 1: median 8 mm; range 4-14; p < 0.0001]. The threshold value of 7 mm was determined using the area under receiver operating characteristic curve of 0.79 [95% confidence interval (CI) 0.69-0.88, p < 0.0001]. In multivariate analysis, AP displacement of ≥7 mm was an independent risk factor for feelings of instability (odds ratio 7.695; 95% CI 2.306-25.674; p = 0.001). CONCLUSIONS: AP laxity of ≥7 mm represents a known cause of feelings of instability. By controlling AP laxity in TKAs, without stiffness in the knee, it is possible to prevent feelings of instability. The clinical relevance is that AP laxity of <7 mm is one of the target areas in TKA. LEVEL OF EVIDENCE: IV.
PURPOSE: Flexion instability following total knee arthroplasty (TKA) is a common indication of early revision. The association between the objective anteroposterior (AP) laxity direction in mid-range flexion and the subjective healing of instability remains unclear; thus, this study aimed to clarify this association. METHODS: In this study, 110 knees (74 females, 92 knees; 16 males, 18 knees) with medial pivot implants were examined with a median age of 79 (range 60-92) years for a median follow-up duration of 22 (range 6-125) months. AP laxity was measured using a KT-1000 arthrometer. Self-reported knee instability score was used for the subjective healing of instability. RESULTS: Eighty-seven knees did not feel unstable (Group 0), whereas 23 knees felt unstable (Group 1). There was a significant difference in AP displacement [Group 0: median 6 mm; range 2-15 mm and Group 1: median 8 mm; range 4-14; p < 0.0001]. The threshold value of 7 mm was determined using the area under receiver operating characteristic curve of 0.79 [95% confidence interval (CI) 0.69-0.88, p < 0.0001]. In multivariate analysis, AP displacement of ≥7 mm was an independent risk factor for feelings of instability (odds ratio 7.695; 95% CI 2.306-25.674; p = 0.001). CONCLUSIONS: AP laxity of ≥7 mm represents a known cause of feelings of instability. By controlling AP laxity in TKAs, without stiffness in the knee, it is possible to prevent feelings of instability. The clinical relevance is that AP laxity of <7 mm is one of the target areas in TKA. LEVEL OF EVIDENCE: IV.
Entities:
Keywords:
Anteroposterior laxity; Mid-flexion instability; Subjective healing of instability; Total knee arthroplasty
Authors: Zhitao Rao; Chaochao Zhou; Willem A Kernkamp; Timothy E Foster; Hany S Bedair; Guoan Li Journal: Knee Surg Sports Traumatol Arthrosc Date: 2019-04-10 Impact factor: 4.342
Authors: Simon C Mears; A Cecilia Severin; Junsig Wang; Jeff D Thostenson; Erin M Mannen; Jeffrey B Stambough; Paul K Edwards; C Lowry Barnes Journal: J Arthroplasty Date: 2022-03-17 Impact factor: 4.435