Total knee arthroplasty with patient-specific instruments improves function and restores limb alignment in patients with extra-articular deformity
Introduction
Alignment is crucial in total knee arthroplasty (TKA) for implant survival and clinical outcome [1], [2], [3]. Both conventional instruments and computer-assisted navigation (CAS) have been used to obtain these objectives [4], [5], [6]. Intra-medullary (IM) instruments recreate the mechanical axis by using the anatomical axis and landmarks [1], [2], [3], [4], [5], [6], [7]. CAS is based on finding the center of the femoral head, the knee and the ankle allowing surgeons to find the mechanical alignment without using the anatomical axes [3], [4]. The use of these navigation systems has resulted in improved alignment [2] but has not completely eliminated outliers or improved clinical outcomes [9], [10]. The area where the advantages of CAS is clear, is in the presence of posttraumatic extra-articular deformities (EAD), retained hardware, ipsilateral long stem total hip arthroplasty or any situation where traditional instrumentation is not feasible [3], [4], [11], [12], [13].
Recently a new instrument for aligning the limb in all three planes, patient-specific instruments (PSI) using MRI or CT-scan, has been developed. Patient-specific positioning guides or cutting blocks are designed from radiological images and are supposed to allow surgeons to improve accuracy in the three planes or the six degrees of freedom of a knee implant [10], [14]. As with navigation, these instruments are based on direct mechanical alignment without using the anatomical axes [3], [4].
Extra-articular deformities have always been a challenge to obtain alignment either by corrective osteotomy or by intra-articular correction of the axis [4], [11], [15], [16]. For these special cases, navigation has proven to be of added value [1], [3], [4], [12], [17]. However, EAD cases can be even more challenging than standard TKA. These complex angular deformity cases ask for experience of the surgeon with the navigation system, especially with the finding of the anatomical landmarks and the technical aspects of correcting EAD via intra-articular resections [13], [17].
In a retrospective multicenter case series, the authors analyzed nine cases of extra-articular deformity and one case of femoral canal obliteration with an internal fixation device, operated with patient-specific instruments (PSI) and intra-articular correction of the alignment using primary implants.
The hypothesis of this study was [1] that PSI restores mechanical limb alignment in total knee arthroplasty with EAD and [2] that PSI assisted TKA for EAD restores function.
Section snippets
Materials and Methods
Between 2008 and 2010, ten patients (6 men and 4 women) with posttraumatic knee arthritis and femoral or tibial canal obliteration or deformity were operated for total knee arthroplasty by 3 of the authors (ET 6; MP 3; MH 1 case). All patients presenting during that consecutive period of time were selected for patient-specific instrumented TKA. At the time of surgery, the mean age of the patients was 58.5 +/− 8.5 years. The average BMI was 33.2 +/− 3.5 kg/m2. Obliterations of the canal were
Results
At a mean follow-up of 3.4 years (range, 2–5 years), the mean Knee Society function score increased from 44 +/− 11 points pre-operatively to 92 +/− 7 points postoperatively (P < 0.05). The mean Knee Society pain score improved from 38 +/− 6 points pre-operatively to 91 +/− 9 points postoperatively (P < 0.05). The Oxford Score improved from a mean 15.6 +/− 5 to 43.5 +/− 4 points (P < 0.05) (Fig. 1).
For all patients, the extension improved from – 7° +/− 3° (range, + 5° to - 11°) to 0° (range, + 2° to − 3°)
Discussion
The most important findings of this study were a statistical improvement in function from preoperative observed for all patients as evidenced by a significant increase in both Knee Society and Oxford Scores and a restoration of the mechanical alignment with PSI in EAD total knee arthroplasty.
Secondary findings of this study were that posttraumatic arthritis patients have reduced pre-operative flexion but that a significant amelioration in flexion can be obtained after TKA. However their
Conclusions
Patient-Specific Instruments are an alternative for conventional instruments and computer-assisted navigation for osteoarthritic knees with extra-articular deformities or retained hardware. Improvement in function and mechanical alignment were obtained at a minimal two years follow-up.
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3D templating and patient-specific instrumentation in primary total knee arthroplasty with retained internal fixation hardware: Two case reports
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A Successful Case of TKA With Complex Deformity And Retained Hardware Using Computer Navigation
2022, Arthroplasty TodayOutcomes of complex primary total knee arthroplasties performed with custom cutting guides
2021, KneeCitation Excerpt :Although questions remain regarding their cost-effectiveness and clinical benefit in un-complicated primary TKAs [8,20–23], custom cutting guides may be a viable option in complex primary TKAs when traditional instrumentation cannot be used or when it would be very challenging to do so. The literature regarding their use in complex TKAs remains limited to three case series that each feature 10 patients or fewer [16–18]. The purpose of this study was to evaluate the use of custom cutting guides in complex primary TKAs for which traditional instrumentation could not be used.