Objectives

Our study aimed to examine if a mobile-bearing total knee replacement (TKR) offered an advantage over fixed-bearing designs with respect to rates of secondary resurfacing of the patella in knees in which it was initially left unresurfaced.

There is conflicting evidence about the merits of mobile bearings in total knee replacement, partly because most randomised controlled trials (RCTs) have not been adequately powered. We report the results of a multicentre RCT of mobile versus fixed bearings. This was part of the knee arthroplasty trial (KAT), where 539 patients were randomly allocated to mobile or fixed bearings and analysed on an intention-to-treat basis. The primary outcome measure was the Oxford Knee Score (OKS) plus secondary measures including Short Form-12, EuroQol EQ-5D, costs, cost-effectiveness and need for further surgery.

There was no significant difference between the groups pre-operatively: mean OKS was 17.18 (sd 7.60) in the mobile-bearing group and 16.49 (sd 7.40) in the fixed-bearing group. At five years mean OKS was 33.19 (sd 16.68) and 33.65 (sd 9.68), respectively. There was no significant difference between trial groups in OKS at five years (-1.12 (95% confidence interval -2.77 to 0.52) or any of the other outcome measures. Furthermore, there was no significant difference in the proportion of patients with knee-related re-operations or in total costs.

In this appropriately powered RCT, over the first five years after total knee replacement functional outcomes, re-operation rates and healthcare costs appear to be the same irrespective of whether a mobile or fixed bearing is used.

Cite this article: Bone Joint J 2013;95-B:486–92.

Most common complication of non-navigated classic total knee arthroplasty (TKA) relates to patella. Not resurfacing the patella makes exposure more difficult in a mini-approach which may add to its potential complications. Effect of navigated mini sub-vastus TKA on native patella is clinically and radiologically studied, observing also, whether severity of deformity or obesity adds to patellae complications in such approach. 92 of 100 subjects were eligible. Peri-operative radiological and navigation data with follow up visits to 24 months provided alignment, patella tilting or displacement data. Clinical outcome gauged by “KSS” documented pain from patella movements, or pain generated from stair climbing, or rising from a chair. Patella is considered subluxated if it displaced ≥ 5mm. No exclusion by obesity or severity of deformity. Results were evaluated with descriptive statistics. Of the 92 patients, 3 had patella pain (3%). 72% had < 5° of patella tilting (of which 3 had patella pain) while 28% had a 5°–17° tilting. As for patellae displacement, 12% displaced laterally (≤3 mm) but with no pain. None had patellar displacement ≥ 4mm (which we define as subluxation), and none had a dislocation. Pre-operative knee deformity ranged from 19° varus to 13° of valgus. 70% of subjects had pre-operative varus/valgus deformity of < 10°. The other 30% had deformity of ≥ 10°. Post-operative mean mechanical axis alignment was 0° (± 1°) with a mean range of motion of −3.8° to 133.6°. No vascular injuries, skin necrosis, deep infection, or fractures. The BMI ranged from 25–46 Kg/m. 2. 16% had a BMI ≥ 40 with no patellar pain, tilting or displacement. Incidence of native patella pain in a navigated mini sub-vastus TKA was low irrespective to body mass or pre-operative deformity. Perhaps navigation helped align the components ideally and thus reducing the complication rate of a mini-approach. However, 28% of native patella tilted > 5° but unlike tilting of a resurfaced patella, it did not correlate with patella pain. In this study, whether non-resurfacing caused the 3% of patella pain is undetermined. Nevertheless, the pain level was not severe to make the patients seek a revision of the patella. Finally, as we compare with other studies, we cannot conclude that mini sub-vastus approach is superior; however its low patella complication rate is comparable if not superior to classic approach

Introduction: Patella baja is the distal positioning of the patella in relation to the femoral condyles in the sagittal plane. True patella baja is due to shortening of the patella tendon (PT), as measured by the Insall-Salvati method, and narrowing of the distance between the patella and the proximal tibia. Pseudo-patella baja describes narrowing of the distance between the patella and the proximal tibia without shortening of the PT and occurs following Total Knee Arthroplasty (TKA), where the tibial prosthesis plus insert are thicker than the resected tibia. Both may cause patella pathology, pain and a reduced range of motion. Pseudo-patella baja can be detected using the Caton-Deschamps method. Soft tissue balancing is an important factor in the success outcome of TKA, but if extensive can necessitate the use of thicker tibial inserts. This may alter the position of the patella in relation to the tibia and increases the risk of creating a pseudo-patella baja. Hypothesis: Patients who undergo extensive soft tissue releases during TKA, with the resultant use of thicker tibial inserts will develop a pseudo-patella baja, and will have a poorer outcome and reduced range of motion. Method: In this prospective study, 506 patients aged 40–90 years underwent 526 Kinemax TKAs, performed by 7 surgeons in 5 centers between October 1999 and December 2002. The extent of soft tissue releases and the size of tibial inserts were recorded. Independent observers used the Caton-Deshamps method to assess patella position measured Pre and post-operative lateral radiographs. The patients were also assessed using the Oxford Knee Score and the American Knee Society Clinical Rating System, with a minimum follow-up of 12 months. Results:. TKA surgery creates a Pseudo-Patella Baja. Excluding patients with a pre-operative patella baja, pseudo patella baja was introduced into 25.6% of patients. (p=0.00). Extensive soft tissue releases during TKA are associated with a 100% increased in the incidence of pseudo patella baja compared to more moderate soft tissue releases. (p=0.002). The use of large tibial inserts is associated with a significant increase in the incidence of pseudo-patella-baja, compared to smaller inserts. Three groups were identified: Small Inserts 8 mm, Medium inserts 10–12mm, and Large inserts 15, 18 & 22 mm. (p=0.042). There was no correlation between the incidence of a pseudo-patella baja and changes in clinical or functional outcome, including range of motion, as measured using the OKS and AKSCRS. Conclusion: Pseudo patella baja occurs in 25% of all patients following TKA, and in over 40% of patients in whom extensive soft tissue releases have been performed and/or large tibial inserts have been used. At 12 months, no detrimental outcomes were attributable to the incidence of pseudo patella baja

Aims: The aim of this study was to investigate the functional results and complications of the total femur prosthesis Endo-Model?. Material and methods:100 total femurs implanted between 3/89 and 9/97 during aseptic revision arthroplasty, all consecutive cases, were included in the study. 87% were female, 13% male. The mean age was 68 years, ranging from 40 to 94. The mean follow-up was 5 years, ranging from one to 12 years. 77% had suffered a complication following implantation of a total hip replacement, 4% of a total knee and 19% following a complication affecting the diaphysis, in most cases a fracture between total hip and total knee prosthesis. From all 100 patients 41% had sustained a periprosthetic fracture preoperatively. Results: As a total femur is a limb saving prosthesis the functional result of hip and knee was assessed according to the Enneking scheme in separate pre- and postoperative evaluations. Preoperative the mean score for hip function was fair, it improved to good postoperatively. For the knee the preoperative score was fair to good, postoperatively better than good. 65% had no complications, deep infection 12%, dislocations 6%, technical faults 3%, patella pain 2%, nerve palsy 1%, secondary wound healing 1%, haematoma 2%, perioperative mortality 3%, not located 5%. Conclusion: The total femur prosthesis Endo-Model? is a valuable limb-saving implant in desolate cases of revision arthroplasty. Meticulous preoperative planning is compulsory. The functional results are surprisingly good. The complication rate is acceptable. To reduce the infection rate we now introduced a perioperative antibiotic prophylaxis