Abstract

Cite this article: Bone Joint Open 2020;1-11:706–708.

Introduction: Uni-compartmental Knee Replacement (UKR) has now become an accepted and widely used treatment for uni-compartmental arthritis. Our unit has performed over 1000 UKRs in the past 22 years. The optimal mechanical design of the implant has yet to be determined.

Method: A prospective trial was commenced in 1999 to compare the short-term results of a fixed bearing with a mobile bearing prosthesis. One hundred and three knees in 95 patients underwent a UKR. Fifty-three had a St Georg Sled fixed bearing prosthesis and 50 had unconstrained mobile bearing Oxford UKR. All were prospectively reviewed using the Oxford and Bristol Knee Scores.

Results: Eighty-four knees have been reviewed at two years with one lost to follow-up. One fixed (2%) and six mobile (12%) bearing knees had been revised. Three fixed bearing and eight mobile bearing knees were dissatisfied because of stiffness or persistent pain and seven mobile bearing knees had undergone further minor procedures, usually for dislocation. At two years, the Bristol and Oxford knee scores for fixed bearing were better than the mobile bearing knees at 90:83 /100 and 38:33 /48 respectively.

Conclusion: There were more early complications in the mobile bearing UKR group, but the functional results were slightly better than in the fixed bearing knees.

Introduction: Lateral uni-compartmental knee replacement (UKR) is seldom indicated and remains controversial. It has been considered a technically challenging operation with variable success. Aim: The aim of this paper is to assess the results of unicompartmental knee replacement using a þxed noncongruous prosthesis. Methods: Eighty-eight knees in 79 patients with lateral unicompartmental osteoarthritis treated with a þxed bearing, non-congruous, fully unconstrained prosthesis. (St Georg Sled UKR) over a period of 21 years by different consultants and there trainees. Surgical approach and rehabilitation protocol varied over this period but there was no change in the surgical indications. Results: At a mean follow up of 9 years (range 2 to 21 years). Fifteen knees had revision surgery (9 for progression of arthritis and 6 for component loosening, 4 for implant breakage and 4 for more than one reason). Six patients complained of moderate or severe pain at þnal follow up. Only þve knees were lost to follow up in the 21-year period. Survivorship analysis was performed on the group using revision for any cause as the end point. At ten years the cumulative survival rate was 83% and at 15 years, when ten knees were still at risk, the cumulative survival rate was 74%. Conclusion: Based on our clinical results and survival rate the St Georg Sled UKR can be considered a suitable treatment for isolated lateral compartment osteoarthritis.

The purpose of this study was to determine the rate of polyethylene wear in a fixed bearing knee replacement in order to establish a norm against which mobile bearing implants can be judged.

Method: Eighteen all polyethylene tibial components were retrieved when a St Georg Sled unicompartmental replacement was being revised. This prosthesis has a biconvex femoral component and a totally flat tibia; thus point loading occurs on at implantation. The implants had been in situ between 6 and 110 months, revision was predominantly for progression of the arthritic process.

Linear wear was measured using an electronic micrometer and volumetric wear by creating a mould of the defect using dental wax, and subsequently weighing the wax.

Results: All components developed dishing which varied in orientation but matched the alignment of the femoral component. A near congruous articulation was thus produced correctly aligned for that particular arthroplasty. The mean linear penetrative wear for the group was 0.33mm (0.09mm per year) and the volumetric wear 124mm³ (26mm³ per year). The rate of wear seemed greatest during the second year.

Conclusion: The wear rate for this totally non congruous implant was much less than anticipated. The linear penetrative wear is comparable to that reported for Charnley hip replacement though more than for a fully congruent mobile UKR. The volumetric wear is much lower than that thought to cause osteolysis. The surprisingly low wear rate suggests that the need for mobile bearing UKRs, with their greater technical demands, should be questioned.

Concomitant ipsilateral femoral and tibial fractures result from high velocity injuries and are often associated with other, life threatening, injuries. They are rare injuries in children with few published series, none of which comment on the use of flexible intramedullary nails in the treatment of such injuries.

We present our experience of concomitant ipsilateral femoral and tibial fractures in children and discuss the use of flexible intramedullary nails in their management.

Hospital records and radiographs of 19 such injuries in 18 patients were studied. These cases were divided into three groups based on the method of treatment. Group A: (8 cases) both the femoral and tibial fractures were internally fixed.

Group B: (4 cases) only one out of the two fractures had internal fixation while the other was externally immobilised.

Group C: (7 cases) both femoral and tibial fractures were treated with external immobilisation like external fixators, plaster cast or traction.

Six cases in group A were treated with flexible intra-medullary nailing The mean age was 8.5 years. The average follow up was 3.5 years. All patients were reviewed and assessed clinically following discharge from hospital.

Patients treated with internal fixation of both fractures had a shorter hospital stay and were able to weight bear earlier. Limb length discrepancy was common in conservatively treated patients. Mean limb length discrepancy was 3.8 cm of shortening. A better range of knee movement was observed in patients treated with flexible nail for femoral and tibial fracture. Over all a good result was achieved in 70% of the patients. Using our assessment criteria we found that Group A faired better than the other two groups on all accounts.

Only a few small series of such a rare injury has been mention in the literature. More complications have been reported in children under 10 years of age. In our study we found better results when both tibial and femoral fractures were treated with internal fixation. The out come results in our patients were not related to age.

We found that internal fixation with closed flexible intramedullary nailing of both femoral and tibial fractures was a safe and effective technique and has therefore been recommended.

Objective: To report the survivorship rate and clinical outcome of a large series of lateral unicompartmental replacements.

Method: 88 lateral St Georg Sled LTKRS were performed between 1978 and 1999. Clinical and radiological data was prospectively recorded at regular follow up and only 5 knees were lost during the 22 year period.

Results: 15 knees were revised after an average of 8 years. (eight for progressive arthritis, six for loosening and four for femoral fracture) 29 patients (30 knees) died during the course of the study. At final follow up (average 9 years) 50 of the 63 remaining knees were rated as good or excellent, nine as fair and nine poor. The mean range of flexion was 110°.

At 10 years the cumulative survival rate was 83% and at 15 years 78% (10 knees at risk). The “worst case scenario” where knees with pain or lost to follow up are added to revisions shows a 10 year survivorship of 74%.

Conclusion: Although the results are not as good as medial UKR. These clinical outcomes suggest that the conservative surgical procedure of lateral UKR with the fixed bearing St George Sled prosthesis can give acceptable results in the uncommon situation of severely symptomatic isolated lateral tibio femoral arthritis.

We describe 88 knees (79 patients) with lateral unicompartmental osteoarthritis which had been treated by the St Georg Sled prosthesis.

At a mean follow-up of nine years (2 to 21) 15 knees had revision surgery, nine for progression of arthritis, six for loosening, four for breakage of a component and four for more than one reason. Six patients complained of moderate or severe pain at the final follow-up. Only five knees were lost to follow-up in the 21-year period.

We performed survivorship analysis on the group using revision for any cause as the endpoint. At ten years the cumulative survival rate was 83%, and at 15 years, when ten knees were still at risk, it was 74%.

Based on our clinical results and survival rate the St Georg Sled may be considered to be a suitable unicompartmental replacement for isolated lateral compartment osteoarthritis.