Limb Lengthening after Primary Total Knee Arthroplasty: Customized Patient-Specific Instrumentation Does Not Affect Expected Limb Lengthening

Abstract

Introduction. Expectations for limb length differences after TKA are important for patient perception and outcomes. Limb length discrepancies may occur due to postoperative leg length increases, which can lead to decreased patient functionality and satisfaction and even possible litigation. The purpose of this study is to examine the frequency and extent of limb lengthening among various preoperative deformities and between two different implant systems. Methods. Preoperative and postoperative full-length standing radiographs were obtained between August 2018 and August 2019 to measure mechanical axis and limb length of operative limbs. Demographic information such as age, sex, and BMI was also collected. Patients were grouped into categories for pre- and postoperative subgroup analysis: valgus, varus, customized implant, and conventional implant. Regression analysis was performed to evaluate significant relationships. Results. Of the 121 primary TKAs analyzed, 62% of the knees showed an increase in limb length after TKA, with an average lengthening of 5.32 mm. Preoperative varus alignment was associated with a mean lengthening of 3.14 mm, while preoperative valgus alignment was associated with a mean lengthening of 16.2 mm. Overall, there were no statistically significant differences in limb lengths pre- and postoperatively ( p = 0.23) and no significant changes in limb length for any subgroup. Further, no variables were associated with limb length changes ( p = 0.49), including the use of customized implants ( p = 0.2). Conclusions. Limb lengthening after TKA is common and, on average, occurs more significantly in valgus knees. No significant difference in limb lengthening could be demonstrated using customized over conventional implants. Preoperative counseling is important to manage patient expectations.

The intraoperative use of a calliper predicts leg length and offset after total hip arthroplasty. Component subsidence influences the leg length

“…Another study reveals that even at the long view, 64% of patients after THA perceive an LLD despite radiologically this is not apparent, setting the threshold for LLD at ≥ 5 mm [ 1 ]. The list of states that can lead to a perception of LLD is long: spine pathology, pelvic obliquity, LLD concerning status post THA, neurological impairment, knee malalignment [ 37 ], and other discrepancies below the hip, leading to a very complex situation. According to the authors, there is an additional time-dependent factor to be considered: the migration of the prosthesis components, which contributes to a change in perception of LLD.…”

Leg Length and Offset After Total Hip Arthroplasty: The Intraoperative use of a Calliper Improves the Results. Should Component Subsidence Influence the Target for Leg Length?

“…Another study reveals that even at the long view 64% of patients after THA perceive a LLD despite radiologically this is not apparent, setting the threshold for LLD at 5 mm [1]. The list of states that can lead to a perception of LLD is long: spine pathology, pelvic obliquity, LLD concerning status post THA, neurological impairment, knee malalignment [35] and other discrepancies below the hip, leading to a very complex situation. According to the authors, there is an additional time dependent factor to be considered: the migration of the prosthesis components, which contributes to a change in perception of LLD.…”

Impact of limb length discrepancy on functional outcome in total knee arthroplasty patients: a prospective cohort study

“…Although multiple factors are associated with poor functional outcome and dissatisfaction, limb length discrepancy (LLD) is a major concern that has been inadequately studied [ 3 – 5 ]. Unlike THA, the principle of TKA involves soft tissue balancing after appropriate bone resection to equalize the flexion-extension gap, and hence limb length alteration is unavoidable [ 5 , 6 ]. Limb length discrepancy has been shown to increase the incidences of back pain, radiculopathy, gait disorders and general dissatisfaction [ 7 – 16 ].…”

“…Only a few studies in the literature evaluated LLD after TKA [ 5 , 6 , 10 , 14 , 15 , 17 – 23 ]. While the western literature reported minimal LLD (< 5.5 mm) that has no clinical relevance [ 6 , 18 – 21 , 23 ], others have reported substantial limb length discrepancy (≥ 10 mm) following unilateral TKA [ 10 , 14 , 15 , 17 ].…”

“…Only a few studies in the literature evaluated LLD after TKA [ 5 , 6 , 10 , 14 , 15 , 17 – 23 ]. While the western literature reported minimal LLD (< 5.5 mm) that has no clinical relevance [ 6 , 18 – 21 , 23 ], others have reported substantial limb length discrepancy (≥ 10 mm) following unilateral TKA [ 10 , 14 , 15 , 17 ]. The LLD issue is more alarming in India and few other Asian countries because of the late presentation, advanced disease with bone defect, ligamentous laxity and proceeding for unilateral TKA despite severe bilateral disease.…”