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Short Term Review After Oxford Medial Unicompartmental Arthroplasty and Total Knee Replacement For Anteromedial Osteoarthritis

*K Periasamy  FRCS, A Mohammed  FRCS(Ortho & Trauma)
RM Venner FRCS

*Specialist Registrar in Orthopaedics and Trauma surgery, Department of Orthopaedics and Trauma surgery, Crosshouse Hospital, Kilmarnock,Scotland,U.K.
Consultant in Orthopaedics and Trauma surgery, Inverclyde Royal Hospital Greenock, Scotland, U.K

Address for Correspondence
Kumar Periasamy, FRCS,
79 D,Shawhill road
, Shawlands, Glasgow, U.K
G41 3RW

'  0141 6490470



We reviewed 14 patients who underwent Oxford Unicompartmental Knee replacement and compared them with 14 patients with Anteromedial compartment Osteoarthritis who underwent Total Knee Replacement. Follow up period ranged from 8 months to 2years 9months(Mean-1year 3months). Outcome was assessed according to Oxford knee score, pain score and range of motion.  No complications occurred. Functional results were the same in the two groups during this period. 

We conclude that there is no difference in short-term results between Oxford Unicompartmental Arthroplasty and Total Knee replacement for Anteromedial Osteoarthritis of Knee.  (Keywords- Anteromedial Osteoarthritis, Oxford Unicompartmental Knee replacement, Total Knee replacement, Outcome, Short-term review)

J.Orthopaedics 2005;2(2)e3



Surgical management of Osteoarthritis confined to the medial compartment of the knee remains a matter of controversy (1). Few studies have compared the outcome of Unicompartmenal Arthroplasty with Total Knee replacement (1), with the same pathology (Anteromedial Osteoarthritis).

Unicompartmenal Arthroplasty for selected cases of OA knee is less invasive, preserving cruciate ligaments, provides better range of motion and more physiological functions (2)(3).

The operation has a lower morbidity, blood transfusion is not required and the implant is cheaper.First Oxford Unicompartmental replacement was performed in 1982(2), which is the natural evolution of the original Meniscal arthroplasty used in 1976(4).

If performed early in the disease process, the operation can arrest the progress of arthritis to the other compartments and provide long-term relief in symptoms (2,13).

The latest Phase 3 OXFORD KNEE is based on the clinical success of its predecessors, which achieved 98 % survival of 10 years with average wear of 0.03mm/year (2,5). Continuous upgrading of the design and strict selection criteria have started to give good results in selected cases. (9,11)


Criteria for Oxford Knee Replacement (2)

1.Both cruciate ligaments must be intact, as stability of the prosthesis depends on the intact cruciate mechanism.

2.Lateral compartment should be well preserved with an intact meniscus and full thickness articular cartilage, best demonstrated by AP x-ray with joint in valgus stress.

3.Superficial fibrillation, marginal osteophyte and localised erosions on the medial margin of lateral condyle are not contraindications.

4.Malalignment of limb should be passively correctable to neutral and not beyond.

5.Flexion deformity should be less than 15 degree and further flexion up to 110 present on EUA.

6.Patello Femoral OA is not a contraindication. In more than 500 cases by Munaj et al  no knee was revised for Patello-Femoral problems.


1. Inflammatory arthritis
Lateral compartment OA.


Patients and method

We had 28 patients in our study.15 were men, 13 women. Age was between 52 to 84 years (Mean-71 years). Follow-up period ranged from 8 months to 2years 9months. (Mean-1 year 3 months) 

Selection of patients:
Between 1998 and 2000, Oxford Knee replacement for Medial compartment Osteoarthritis was performed in 18 patients by the senior author in Inverclyde Royal Hospital which is a District General hospital.  14 patients were available for follow-up in this group. 

We obtained X-rays and case notes of patients who underwent Total Knee Replacement during the same period by two different firms in the same hospital, who did not use the unicompartmental knee replacement at the time of the study. The senior author individually reviewed every X-ray.  We selected the patients who had Medial compartment Osteoarthritis whom would have been considered for an Oxford Medial Unicompartmental Arthroplasty by the senior author according to the radiological criteria, (2,7,15). The total number in this group was 14. Further confirmation was made after reviewing the case notes to confirm the operative findings correlated with the radiological findings. 

Operative technique:
The senior author performed the Oxford knee replacements. Medial minimal incision technique was used in majority of the patients.  Intra operative findings were recorded and minor erosions in the lateral femoral condyle and patello-femoral joints were ignored.  Phase 3 components were used. Palacos cement was used in both groups.

Two different consultants carried out the Total Knee Replacements. Midline incision was used, medial Para patellar approach for Arthrotomy.  Kinemax (Stryker-Howmedica) prosthesis was used in all 14 patients.  Hospital stay in both groups averaged between 5-7 days. 

Review of patients:
All 28 patients were contacted by post and reviewed individually in a special clinic arranged exclusively for this study.  Patients were first seen by a Specialist nurse and the Oxford scores and Pain scores were recorded, further reviewed by the first author for examination. We decided to use the Oxford scoring and the pain score alone because these were the only pre-op scores recorded in all patients.  Of the 4 patients not available for follow up 2 had moved out of the area, 1 patient had a total knee replacement on the opposite side and was excluded from the study.1 patient was too frail and declined to attend the clinic. 

Data analysis:
Data was analysed using Microsoft Excel, Independent t tests and Paired t tests.


Of the 28 patients reviewed in the clinic all except 1 patient (post-op- pain score –6/10) had excellent pain relief following the procedures.

Mean pre-op pain score- Oxford-8.71, TKR-9.43, p=0.082, no significant difference.

Mean post-op pain score-Oxford-1.43, TKR-1.86, p=0.364, no significant difference.

The mean range of movement in the Oxford knee group was 3-110 degrees (Range of flexion-95-125), TKR was 2.5-105 degrees (Range of flexion-70-125). The one patient with persistent pain had a good range of movement and function, an obvious cause was not found so far.

Oxford scores:

We assessed the knee functional scores with the validated Oxford knee scoring system (1,16). We are aware of the controversies using this scoring system. We still think it is a good reflection of the patient perception of function.

Mean pre-op for Oxford – 42.25, TKR-47.50,p=0.262,no significant difference.

Mean post-op for Oxford- 20.36, TKR-23.71, p=0.292 no significant difference.

Radiographic assessment:

No significant loosening was seen in either tibial or femoral components in all the patients. So far none have had revision surgery.

4 patients were not available for follow-up in the Oxford Group .We did not receive any information from the General Practitioner about the current status of these 2 patients who have moved out of the area. We know that the remaining 2 patients had no problems with their knee through telephonic conversation. 

Results of the independent and paired t-tests:

Independent t-tests
Age by sex – Mean age of females = 71; males = 72 \no significant diff p=0.672

Age by type of knee replacement – Mean age of OKR patients = 71; TKR = 71\no significant difference p=0.981

Pre-pain by type of knee replacement - Mean pre-pain score of OKR patients  = 8.71; TKR = 9.43\no significant difference p=0.082

Post-pain by type of knee replacement - Mean post-pain score of OKR patients  = 1.43; TKR = 1.86\no significant difference p=0.364

Oxford pre-pain by type of knee replacement - Mean pain score of OKR patients  = 42.25; TKR = 47.50\no significant difference p=0.262

Oxford post-pain by type of knee replacement - Mean pain score of OKR patients  = 20.36; TKR = 23.71\no significant difference  p=0.292 

Paired t-test
Pre -0p pain compared with Post-Op pain 

All patients – mean pre-pain score = 9.07; mean post score = 1.64 \ significant diff p=0.000

OKR patients – mean pre-pain score = 8.71; mean post score = 1.43\ significant diff p=0.000

TKR patients – mean pre-pain score = 9.43; mean post score = 1.86\ significant diff p=0.000 

Oxford pre pain score compared with oxford post pain 

All patients – mean pre-pain score = 44.5; mean post score = 21.14 \ significant diff p=0.000

OKR patients – mean pre-pain score = 42.25; mean post score = 20.88\ significant diff p=0.000

TKR patients – mean pre-pain score = 47.5; mean post score = 21.55\ significant diff p=0.001


Discussion & Conclusions

There are very few comparative studies of Uni-compartment knee replacements compared with total knee replacements in the literature.  Newman et al (10) reported results on prospective randomised study of 110 knees comparing Uni-compartmental replacements and total knee replacements, without any significance between the groups.  They used the St George sleg knee. 

Figure 1A.  Pre op AP xray of knee with Anteromedial Osteoarthritis

There was a small increased range of motion in the Uni-compartmental group as expected.  Weale et al (1) showed that neither pain nor function al outcomes were significantly different, although the Uni-compartmental group were better able to climb stairs. 

Figure 1B.  Pre op LAT xray of knee with Anteromedial Osteoarthritis

This study however, compared two different pathologies i.e. Anteromedial Osteoarthritis and more extensive Osteoarthritis of the knee.  Past studies took advantage of the fact that at the time of the study only one of the surgeons at Inverclyde Royal Infirmary was undertaking hemiarthroplasty for Anteromedial Osteoarthritis.  The other two consultants concerned in the study utilised a total knee replacement Kinemax in all patients with Osteoarthritis of the knee. 

Figure 2A.  Post op AP xray following Total Knee replacement.

Our study was to determine if there was any difference in the results of outcome in the different procedures for the same pathology i.e. Anteromedial Osteoarthritis.Total Knee replacement is an established and time proven procedure for both Bicondylar and Unicondylar arthritis (10).

Figure 2B.  Post op LAT xray following Total Knee replacement

Our results show that there is no significant difference in results of both procedures for Anteromedial Osteoarthritis of the knee in the short term. We plan to proceed with a long-term review to establish any difference in the results.

Figure 3A.  Pre op AP xray Anteromedial Osteoarthritis.

Figure 3B.  Pre op LAT xray Anteromedial Osteoarthritis.

Although this is a retrospective study of relatively small numbers, it does focus entirely on Anteromedial Osteoarthritis of the knee and the short-term results clearly demonstrate that there is no difference in the short-term results and therefore at this moment in time justifies the continued use of a hemiarthroplasty for Anteromedial Osteoarthritis of the knee.

Figure 4A.  Post op AP xray Oxford knee replacement

Figure 4B.  Post op LAT xray Oxford knee replacement


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 This is a peer reviewed paper 

Please cite as :

K Periasamy:Short Term Review After Oxford Medial Unicompartmental Arthroplasty and Total Knee Replacement For Anteromedial Osteoarthritis
J.Orthopaedics 2005;2(2)e3





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