Frontal Plane Analysis During Lunging After Knee Replacement Surgeries

Abstract

It is reported that 70% of the Knee OA patients have cartilage degeneration isolated to the medial and patellofemoral (PF) compartments. Majority of these patients receive total knee replacements (TKR). The iDuo knee is a customized, individually made bi-compartmental knee replacement (BKR) treating OA at medial/lateral and PF compartments. The BKR keeps the contra-lateral compartment intact, retains the anterior and posterior cruciate ligaments, and regains normal knee geometry with good knee alignment. Thus, the BKR knee could have similar knee mechanics to that of a normal healthy knee. To date, there is no information regarding the mechanics during daily activities (e.g. lunging) with a BKR. There are no in vivo biomechanical comparisons between a BKR and a limb with an off-the-shelf TKR. PURPOSE: To examine differences in frontal plane knee moment between three participant groups during a lunging exercise: (1) BKR, (2) TKR, and (3) healthy controls. METHODS: To date, 21 participants have been tested, which included 5 TKR patients (66±12 yr.; 105±42 kg; 1.75±0.12 m) (Persona, Zimmer Inc.) (post-op: 11±4 mo.), 4 BKR patients (63±7 yr.; 93±18 kg; 1.66±0.06 m) (iDuo, ConforMIS Inc.) (post-op: 21±3 mo.), and 12 healthy controls (57±6 yr.; 82±12 kg; 1.75±0.11 m). 3D motion data (100Hz) and ground reaction forces (2000Hz) were collected during forward lunges. Peak internal knee abduction moments (ABDM) were calculated during both the down and up phases of a lunge. Student t tests were performed. α = 0.05. RESULTS: he means ± SDs of the ABDM of the BKR, TKR, and control participants were: 0.10±0.03, 0.15±0.06, 0.11±0.10 Nm/kg during down phase, respectively; and 0.11±0.05, 0.23±0.13, 0.08±0.09 Nm/kg during up phase, respectively. No differences were found between the BKR and control participants for either the down (p=0.43) or up phases (p=0.31). The TKR patients showed greater ABDM than the controls during the up phase (p=0.01). There was a trend that the BKR was associated with smaller ABDM than the TKR (p=0.06). CONCLUSION: Normal frontal plane mechanics appear to be achievable outcomes with customized BKR surgeries. BKR patients demonstrated similar frontal plane mechanics to the healthy controls during lunging. Off-the-shelf TKR patients showed significantly different mechanics from healthy controls.