Tilman Walker

Mobile-bearing lateral unicompartmental knee replacement with the Oxford domed tibial component

The Oxford mobile-bearing unicompartmental knee replacement (UKR) is an effective and safe treatment for osteoarthritis of the medial compartment. The results in the lateral compartment have been disappointing due to a high early rate of dislocation of the bearing. A series using a newly designed domed tibial component is reported. The first 50 consecutive domed lateral Oxford UKRs in 50 patients with a mean follow-up of three years (2.0 to 4.3) were included. Clinical scores were obtained prospectively and Kaplan-Meier survival analysis was performed for different endpoints. Radiological variables related to the position and alignment of the components were measured. One patient died and none was lost to follow-up. The cumulative incidence of dislocation was 6.2% (95% confidence interval (CI) 2.0 to 17.9) at three years. Survival using revision for any reason and aseptic revision was 94% (95% CI 82 to 98) and 96% (95% CI 85 to 99) at three years, respectively. Outcome scores, visual analogue scale for pain and maximum knee flexion showed a significant improvement (p < 0.001). The mean Oxford knee score was 43 (SD 5.3), the mean Objective American Knee Society score was 91 (SD 13.9) and the mean Functional American Knee Society score was 90 (SD 17.5). The mean maximum flexion was 127° (90° to 145°). Significant elevation of the lateral joint line as measured by the proximal tibial varus angle (p = 0.04) was evident in the dislocation group when compared with the non-dislocation group. Clinical results are excellent and short-term survival has improved when compared with earlier series. The risk of dislocation remains higher using a mobile-bearing UKR in the lateral compartment when compared with the medial compartment. Patients should be informed about this complication. To avoid dislocations, care must be taken not to elevate the lateral joint line.

10-year results of the uncemented Allofit press-fit cup in young patients.

Background and purpose — Uncemented acetabular components in primary total hip arthroplasty (THA) are commonly used today, but few studies have evaluated their survival into the second decade in young and active patients. We report on a minimum 10-year follow-up of an uncemented press-fit acetabular component that is still in clinical use. Methods — We examined the clinical and radiographic results of our first 121 consecutive cementless THAs using a cementless, grit-blasted, non-porous, titanium alloy press-fit cup (Allofit; Zimmer Inc., Warsaw, IN) without additional screw fixation in 116 patients. Mean age at surgery was 51 (21–60) years. Mean time of follow-up evaluation was 11 (10–12) years. Results — At final follow-up, 8 patients had died (8 hips), and 1 patient (1 hip) was lost to follow-up. 3 hips in 3 patients had undergone acetabular revision, 2 for deep infection and 1 for aseptic acetabular loosening. There were no impending revisions at the most recent follow-up. We did not detect periacetabular osteolysis or loosening on plain radiographs in those hips that were evaluated radiographically (n = 90; 83% of the hips available at a minimum of 10 years). Kaplan-Meier survival analysis using revision of the acetabular component for any reason (including isolated inlay revisions) as endpoint estimated the 11-year survival rate at 98% (95% CI: 92–99). Interpretation — Uncemented acetabular fixation using the Allofit press-fit cup without additional screws was excellent into early in the second decade in this young and active patient cohort. The rate of complications related to the liner and to osteolysis was low.

Sports, Physical Activity and Patient-Reported Outcomes After Medial Unicompartmental Knee Arthroplasty in Young Patients.

One hundred-and-one patients age 60 or younger following medial mobile bearing UKA were reviewed retrospectively with a minimum follow-up of 2 years using the Schulthess activity score, Tegner, UCLA and SF-36 score to assess their level of physical activity and quality of life. Patients showed a rapid recovery and resumption of their activities with a return-to-activity rate of 93%. Most common activities were low impact, whereas high-impact activities showed a significant decrease. Precaution was found to be the main reason for a decrease in the level of activity. The results of this study demonstrate that patients age 60 or younger following medial UKA were able to return to regular physical activities with almost two-thirds of the patients reaching a high activity level (UCLA≥7).

Cementless Oxford medial unicompartimental knee replacement: an independent series with a 5-year-follow-up

PurposeCemented unicompartmental knee replacement (UKR) has proven excellent long-term survival rates and functional scores in Price et al. (Clin Orthop Relat Res 435:171–180, 2005), Price and Svard (Clin Orthop Relat Res 469(1):174–179, 2011) and Murray et al. (Bone Joint Surg Br 80(6):983–989, 1998). The main causes for revision, aseptic loosening and pain of unknown origin might be addressed by cementless UKR in Liddle et al. (Bone Joint J 95-B(2):181–187, 2013), Pandit et al. (J Bone Joint Surg Am 95(15):1365–1372, 2013), National Joint Registry for England, Wales and Northern Ireland: 10th Annual Report 2013 (http://www.njrcentre.org.uk/njrcentre/Portals/0/Documents/England/Reports/10th_annual_report/NJR%2010th%20Annual%20Report%202013%20B.pdf, 2013), Swedish Knee Arthroplasty Register: Annual Report 2013 (http://www.myknee.se/pdf/SKAR2013_Eng.pdf, 2013).MethodsThis single-centre retrospective cohort study reports the 5-year follow-up results of our first 30 consecutively implanted cementless Oxford UKR (OUKR). Clinical outcome was measured using the OKS, AKSS, range of movement and level of pain (visual analogue scale). The results were compared to cemented OUKR in a matched-pair analysis.ResultsImplant survival was 89.7%. One revision each was performed due to tibial fracture, progression of osteoarthritis (OA) and inlay dislocation. The 5-year survival rate of the cementless group was 89.7% and of the cemented group 94.1%. Both groups showed excellent postoperative clinical scores.ConclusionsCementless fixation shows good survival rates and clinical outcome compared to cemented fixation.

Results after Cementless Medial Oxford Unicompartmental Knee Replacement - Incidence of Radiolucent Lines

Purpose Tibial radiolucent lines (RL) are commonly seen in cemented unicompartmental knee replacement (UKR). In the postoperative course, they can be misinterpreted as signs of loosening, thus leading to unnecessary revision. Since 2004, a cementless OUKR is available. First studies and registry data have shown equally good clinical results of cementless OUKR compared to the cemented version and a significantly reduced incidence of RL in cementless implants. Methods This single-centre retrospective cohort study includes the first 30 UKR (27 patients) implanted between 2007 and 2009 with a mean follow-up of 5 years. Clinical outcome was evaluated using the OKS, AKS, range of movement (ROM) and level of pain (VAS). Standard radiologic evaluation was performed at three months, one and five years after surgery. The results five years after implantation were compared to a group of 27 cemented Oxford UKR (OUKR) in a matched-pair-analysis. Results Tibial RL were seen in 10 implants three months after operation, which significantly decreased to five after one year and to three after five years (p = 0.02). RL did not have a significant influence on revision (p = 1.0) or clinical outcome after five years. RL were always partial, never progressive and strictly limited to the tibia. There was no significant difference in the incidence of tibial RL five years after implantation between cemented and cementless implants (cemented: 4, cementless: 3, p = 1.0). Conclusions After cementless implantation RL were limited to the tibia, partial and never progressive. During short term follow-up the incidence of RL decreased significantly. RL seem to have no influence on clinical outcome and revision.

Mid-term results of lateral unicondylar mobile bearing knee arthroplasty: a multicentre study of 363 cases

Aims The aim of this independent multicentre study was to assess the mid‐term results of mobile bearing unicondylar knee arthroplasty (UKA) for isolated lateral osteoarthritis of the knee joint. Patients and Methods We retrospectively evaluated 363 consecutive, lateral UKAs (346 patients) performed using the Oxford domed lateral prosthesis undertaken in three high‐volume knee arthroplasty centres between 2006 and 2014. Mean age of the patients at surgery was 65 years (36 to 88) with a mean final follow‐up of 37 months (12 to 93) Results A total of 36 (10.5%) patients underwent revision surgery, giving a survival rate of 90.1% at three years (95% confidence intervals (CI) 86.1 to 93.1; number at risk: 155) and 85.0% at five years (95% CI 77.9 to 89.9; number at risk: 43). Dislocation of the mobile bearing occurred in 18 patients (5.6%) at three years (95% CI 1.0 to 16.4; number at risk: 154) and in 20 patients (8.5%) at five years (95% CI 1.0 to 27.0; number at risk: 42). There were no significant differences in the dislocation rate between the participating centres or the surgeons. We were not able to identify an effect of each surgeons learning curve on the dislocation rate of the mobile bearing. The clinical outcome in patients without revision surgery at final followup was good to excellent, with a mean Oxford knee score of 40.3 (95% CI 39.4 to 41.2), a mean Tegner activity score of 3.2 (95% CI 3.1 to 3.3) and a mean University of California, Los Angeles score of 5.7 (95% CI 5.5 to 5.9). Conclusion Our data, which consists of a high number of patients treated with mobile bearing UKA in the lateral compartment, indicates a high revision rate of 15% at five years with dislocation of the mobile bearing being the main reason for implant failure. Despite the good functional and clinical results and the high patient satisfaction in our study group, we therefore discontinued using mobile‐bearing lateral UKA in favour of a fixed‐bearing component.