Early outcomes of a modern cemented total knee arthroplasty : is tibial loosening a concern?

AIMS

Recent total knee arthroplasty (TKA) designs have featured more anatomical morphologies and shorter tibial keels. However, several reports have raised concerns about the impact of these modifications on implant longevity. The aim of this study was to report the early performance of a modern, cemented TKA design.

METHODS

All patients who received a primary, cemented TKA between 2012 and 2017 with a minimum two-year follow-up were included. The implant investigated features an asymmetrical tibial baseplate and shortened keel. Patient demographic details, Knee Society Scores (KSS), component alignment, and the presence of radiolucent lines at final follow-up were recorded. Kaplan-Meier analyses were performed to estimate survivorship.

RESULTS

A total of 720 of 754 primary TKAs (95.5%) were included with a mean follow-up of 3.9 years (SD 1.3); 562 (78.1%) were cruciate-retaining and 158 (21.9%) were posterior-stabilized. A total of 11 (1.5%) required reoperation for periprosthetic joint infection and seven (1.0%) for aseptic tibial loosening (five cruciate-retaining, two posterior-stabilized). Loosening occurred at a mean of 3.3 years (0.9 to 6.5). There were no cases of loosening in the 33 patients who received a 14 mm × 30 mm tibial stem extension. All-cause survivorship was 96.6% at three years (95% confidence interval (CI) 95.3% to 98.0%) and 96.2% at five years (95% CI 94.8% to 97.7%). Survivorship with revision for aseptic loosening was 99.6% at three years (95% CI 99.1% to 100.0%) and 99.1% at five years (95% CI 98.4% to 99.9%). Tibial components were in significantly more varus in those with aseptic loosening (mean 3.4° (SD 3.7°) vs 1.3° (SD 2.0°); p = 0.015). There were no other differences in demographic, radiological, or surgical characteristics between revised and non-revised TKAs for aseptic loosening (p = 0.293 to 1.00). Mean KSS improved significantly from 57.3 (SD 9.5) preoperatively to 92.6 (SD 8.9) at the final follow-up (p < 0.001).

CONCLUSION

This is the largest series to date of this design of implant. At short-term follow-up, the rate of aseptic tibial loosening is not overly concerning. Further observation is required to determine if there will be an abnormal rate of loosening at mid- to long-term follow-up. Cite this article: Bone Joint J 2021;103-B(6 Supple A):51-58.

Does Femoral Morphology Predict the Risk of Periprosthetic Fracture After Cementless Total Hip Arthroplasty?

BACKGROUND

Periprosthetic femur fracture remains a leading mode of early failure following cementless total hip arthroplasty (THA). The purpose of this study is to determine if a specific femoral morphology is associated with an increased risk of acute, periprosthetic fracture after cementless THA.

METHODS

An institutional arthroplasty registry was used to identify 32 primary, cementless THAs revised for acute, postoperative periprosthetic fracture ("fracture" cohort) within 3 months of the index procedure. Patients were matched 1:2 to 64 THAs without fracture ("control" cohort) for age, body mass index, gender, and stem design. Preoperative radiographic measurements performed on anteroposterior pelvis and femur radiographs included the neck-shaft angle, endosteal width at 4 locations, and external cortical diameter at 2 locations. These measurements were used to calculate the morphological cortical index, canal flare index, canal calcar ratio, and canal bone ratio. Postoperative measurements included canal fill and stem alignment. Statistical analyses included clustered regressions, Fisher's exact test, and Student's t-test.

RESULTS

The mean endosteal width at 10 cm distal to the lesser trochanter was greater in fracture patients, although not statistically significant (P = .1). However, this resulted in differences in the canal flare index (P = .03), canal calcar ratio (P = .03), and canal bone ratio (P = .03) between the 2 cohorts. These ratios indicate decreased meta-diaphyseal taper in fracture patients. Preoperative femoral neck-shaft angle was more varus in fracture patients (P = .04).

CONCLUSION

Patients sustaining an acute, periprosthetic fracture with cementless femoral fixation after THA had thinner distal cortices and a decreased meta-diaphyseal taper.

Restoration of peak strength and endurance following distal biceps reconstruction with allograft for chronic ruptures

BACKGROUND

Distal biceps reconstruction for chronic rupture often requires a graft to recover length and allow for distal tendon reattachment to bone. Our purpose was to assess peak strength and endurance recovery following biceps reconstruction with tendon grafts.

HYPOTHESIS

We hypothesized that allograft reconstruction would result in decreased flexion and supination peak strength and endurance.

METHODS

Consecutive distal biceps reconstructions with allograft, performed for chronic ruptures between January 2008 and March 2018 at a single institution, were reviewed. Isokinetic dynamometry for peak strength and endurance testing was performed on the operative and contralateral arms in flexion and supination. Functional outcomes and overall satisfaction with the operation were determined.

RESULTS

Eleven patients were available for a complete evaluation, including dynamometry, at a mean of 46 months postoperatively. Reconstructions demonstrated a nonsignificant trend toward decreased peak flexion strength (P = .06), and significantly decreased peak supination strength (P = .01) compared with the unaffected arm. There were no differences in flexion and supination endurance between the affected and unaffected arms. Using standardized outcome scales, patients reported excellent function.

CONCLUSION

Chronic biceps ruptures undergoing reconstruction are highly functional and patients are satisfied. Somewhat surprisingly, supination and flexion endurance were equal to the contralateral, uninvolved arm. However, this procedure does not restore peak supination strength.