Abstract
Introduction
Stiffness after total knee arthroplasty (TKA) has been reported to occur due to component malpositioning and/or oversizing, improper femoral component (FC) flexion and tibial component (TC) slope, tight extension gap, inaccurate joint line placement, deficient posterior osteophyte resection, heterotopic ossification (HO), poor patellofemoral joint reconstruction, poor posterior condylar offset restoration, and/or posterior cruciate ligament (PCL) under-resection or retraction. However, the importance of these potential factors for stiffness are not well documented in the medical literature. The aim of this study was therefore to evaluate specific radiographic parameters in patients who had stiffness after primary TKA.
Material and Methods
An IRB-approved retrospective chart review was performed to identify patients that were revised due to stiffness after TKA. We defined stiffness as 15º or more of flexion contraction, less than 75º of flexion or a range of motion (ROM) of 90º with the chief complaint of limited ROM and pain. Patients with history of previous revisions and/or ORIF, infection, or isolated polyethylene exchange were excluded. Patients with a minimum of 1 year radiographic follow-up were included. Radiographic measurements were performed as described by the Knee Society TKA Roentgenographic Evaluation System (KSRES). Two blinded observers performed all measurements. Descriptive data is reported as mean (range). Inter-observer correlations were reported using Intraclass correlations coefficient (ICC).
Results
A total of 44 patients met the inclusion criteria. Of those, 13 (30%) were male and 31 (70%) were female. Mean BMI was 33.9 kg/m2 (19.5–58). ICCs ranged from good to excellent (>0.8) for all measurements performed. Coronal FC and TC alignments were 95.29º (82.4º–100.6º) and 89.16º (84.4º–94.2º) respectively. HO ranged from 0 to 3 (0:43%, 1:36%, 2:11%, 3:10%). FC-Flexion and TC-slope were 10.17 (3.5–19.8) and 86.7 (61.2–99.2) respectively. Insall-Salvati ratio was 1.01 (0.58–2.04). Posterior condylar offset (CO) ratio was 0.51 (0.34–1.11). Anterior CO ratio was 0.2 (0–0.34). Anterior femoral cortex notching ranged from 0 to 3 (0:39%, 1:43%, 2:14%, 3:4%). Femoral posterior osteophytes were observed in 32% of patients. A gap between the anterior flange and the femoral cortex was observed in 45% of patients. The patella was resurfaced in 93% of patients with a mean patellar tilt and patellar displacement of 5.34º (−8.9º to 5.34º) and 9.88% (−5 to 41%) respectively.
Conclusion
To our knowledge this is the first study reporting specific radiographic data on postoperative stiffness following primary TKA. From the observed radiographic measurements, the increased mean femoral component flexion, the high amount of postoperative HO and posterior osteophytes, and the anterior cortical and component gap suggest possible risk factors influencing the occurrence of postoperative stiffness. Future focus will include a matched control population of patients in order to establish statistical significance of all observed values.
