Christopher Dodd

Does body mass index affect the outcome of unicompartmental knee replacement

BACKGROUND Obesity is considered to be a contraindication for unicompartmental knee replacement (UKR). The aim was to study the impact of BMI on failure rate and clinical outcome of the Oxford mobile bearing UKR. METHOD Two thousand four hundred and thirty-eight medial Oxford UKRs were studied prospectively and divided into groups: BMI<25 (n=378), BMI 25 to <30 (n=856), BMI 30 to <35 (n=712), BMI 35 to <40 (n=286), and BMI 40 to <45 (n=126) and BMI≥45 (n=80). RESULTS There was no significant difference in survival rate between groups. At a mean follow-up of 5years (range 1-12years) there was no significant difference in the Objective American Knee Society Score between groups. There was a significant (p<0.01) trend with the Oxford Knee Score (OKS) and Functional American Knee Society Scores decreasing with increasing BMI. As there was an opposite trend (p<0.01) in pre-operative OKS, the change in OKS increased with increasing BMI (p=0.048). The mean age at surgery was significantly (p<0.01) lower in patients with higher BMI. CONCLUSIONS Increasing BMI was not associated with an increasing failure rate. It was also not associated with a decreasing benefit from the operation. Therefore, a high BMI should not be considered a contra-indication to mobile bearing UKR. LEVEL OF EVIDENCE IV.

Changes in muscle torque following anterior cruciate ligament reconstruction: A comparison between hamstrings and patella tendon graft procedures on 45 patients

We designed a prospective study to examine the influence of graft type (hamstring or patella tendon) on thigh muscle torque recovery after anterior cruciate ligament reconstruction. 60 patients undergoing ACL reconstruction, using a hamstring or patella tendon graft, were studied and 45 were followed up to 1 year. Concentric and eccentric quadriceps and hamstring torque were recorded, using an isokinetic dynamometer preoperatively, 6 and 12 months after ACL reconstruction. We found an improvement in all muscle functions in both the operated and unoperated legs during the recovery period. Graft type had no effect on recovery. During the first 6 months, torque was restored to preoperative levels and continued to improve in all muscles and actions between 6 months and 1 year.

Total knee arthroplasty fixation. Comparison of the early results of paired cemented versus uncemented porous coated anatomic knee prostheses.

The results of 18 matched pairs of Porous Coated Anatomic knee prostheses were studied to compare the early clinical and functional performance of cemented versus uncemented fixation with an average five-year follow-up period for both. The knee score improved from a preoperative average of 35 points to a postoperative average of 90 points in the cemented group, and from 38 points to 93 points in the uncemented group. In particular, the individual pain scores and the range-of-motion values were well matched at the three-, six-, and 12-month follow-up visits and showed a steady improvement. Subjectively, all patients were pleased with the results of surgery; one-third preferred the cemented side, one-third preferred the uncemented side, and one-third found no difference in the performance of either knee. The clinical and functional performance of knee prostheses in patients who had one cemented knee and one uncemented knee were comparable and possibly unrelated to the type of fixation method.

Oxford medial unicompartmental arthroplasty for focal spontaneous osteonecrosis of the knee.

Background Spontaneous osteonecrosis of the knee (SONK) is a distinct clinical condition occurring in patients without any associated risk factors. There is controversy as to the best method of treatment, and the available literature would suggest that patients with SONK have a worse outcome than those with primary osteoarthrosis when arthroplasty is performed. We assessed the outcome of medial unicompartmental knee arthroplasty (UKA) using the Oxford prosthesis for end-stage focal spontaneous osteonecrosis of the knee (SONK; Ahlbäck grades III & IV). Patients and methods We assessed 29 knees (27 patients) with spontaneous osteonecrosis of the knee using the Oxford Knee Score. 26 knees had osteonecrosis of the medial femoral condyle and 3 had osteonecrosis of the medial tibial plateau. All had been operated on using the Oxford Medial Unicompartmental Knee Arthroplasty (UKA). This group was compared to a similar group (28 knees, 26 patients) who had undergone the same arthroplasty, but because of primary osteoarthrosis. Patients were matched for age, sex and time since operation. The mean length of follow-up was 5 (1–13) years. Results There were no implant failures in either group, but there was 1 death (from unrelated causes) 9 months after arthroplasty in the group with osteonecrosis. The mean Oxford Knee Score in the group with osteonecrosis was 38, and it was 40 in the group with osteoarthrosis. Interpretation Use of the Oxford Medial UKA for spontaneous focal osteonecrosis of the knee is reliable in the short to medium term, and gives results similar to those obtained when it is used for patients with primary osteoarthrosis.

Medial unicompartmental arthroplasty after failed high tibial osteotomy

Satisfactory selection criteria are essential for the successful outcome of unicompartmental knee arthroplasty (UCA). We report the frequency of revision of the Oxford medial unicompartmental arthroplasty in knees previously treated for anteromedial osteoarthritis by high tibial osteotomy (HTO). The combined results from three sources were used to allow statistical analysis of this uncommon subgroup. In the combined series of 631 knees (507 patients) which had medial unicompartmental replacement, 613 were primary procedures and 18 were for a failed HTO. The mean follow-up times of the two groups were similar (5.8 years and 5.4 years, respectively). At review, 19 (3.1%) of the primary procedures and five (27.8%) of those undertaken for a failed HTO had been revised to total knee replacement. Survival analysis revealed the ten-year cumulative survivals to be 96% and 66%, respectively. The log-rank comparison of these survivals revealed a highly significant difference (p < 0.0001). We recommend that the Oxford UCA should not be used in knees which have previously undergone an HTO.

Cemented versus cementless Oxford unicompartmental knee arthroplasty using radiostereometric analysis: a randomised controlled trial.

The most common reasons for revision of unicompartmental knee arthroplasty (UKA) are loosening and pain. Cementless components may reduce the revision rate. The aim of this study was to compare the fixation and clinical outcome of cementless and cemented Oxford UKAs. A total of 43 patients were randomised to receive either a cemented or a cementless Oxford UKA and were followed for two years with radiostereometric analysis (RSA), radiographs aligned with the bone-implant interfaces and clinical scores. The femoral components migrated significantly during the first year (mean 0.2 mm) but not during the second. There was no significant difference in the extent of migration between cemented and cementless femoral components in either the first or the second year. In the first year the cementless tibial components subsided significantly more than the cemented components (mean 0.28 mm (sd 0.17) vs. 0.09 mm (sd 0.19 mm)). In the second year, although there was a small amount of subsidence (mean 0.05 mm) there was no significant difference (p = 0.92) between cemented and cementless tibial components. There were no femoral radiolucencies. Tibial radiolucencies were narrow (< 1 mm) and were significantly (p = 0.02) less common with cementless (6 of 21) than cemented (13 of 21) components at two years. There were no complete radiolucencies with cementless components, whereas five of 21 (24%) cemented components had complete radiolucencies. The clinical scores at two years were not significantly different (p = 0.20). As second-year migration is predictive of subsequent loosening, and as radiolucency is suggestive of reduced implant-bone contact, these data suggest that fixation of the cementless components is at least as good as, if not better than, that of cemented devices.

Unicompartmental knee arthroplasty: is the glass half full or half empty?

There is a large amount of evidence available about the relative merits of unicompartmental and total knee arthroplasty (UKA and TKA). Based on the same evidence, different people draw different conclusions and as a result, there is great variability in the usage of UKA. The revision rate of UKA is much higher than TKA and so some surgeons conclude that UKA should not be performed. Other surgeons believe that the main reason for the high revision rate is that UKA is easy to revise and, therefore, the threshold for revision is low. They also believe that UKA has many advantages over TKA such as a faster recovery, lower morbidity and mortality and better function. They therefore conclude that UKA should be undertaken whenever appropriate. The solution to this argument is to minimise the revision rate of UKA, thereby addressing the main disadvantage of UKA. The evidence suggests that this will be achieved if surgeons use UKA for at least 20% of their knee arthroplasties and use implants that are appropriate for these broad indications. Cite this article: Bone Joint J 2015;97-B(10 Suppl A):3–8.

Sensorimotor changes after anterior cruciate ligament reconstruction.

The restoration of joint stability is unlikely to be dependent on passive properties of the joint alone, yet the effect of anterior cruciate ligament reconstructive surgery on the sensorimotor system largely remains unexplored. This study evaluated whether surgical reconstruction of the ligament had any effect on one indicator of sensorimotor function, hamstring contraction latency, which previously has been shown to be related to function. Twenty-five patients with unilateral chronic anterior cruciate ligament deficiency had measures of hamstring contraction latency obtained before and after (3 and 6 months) reconstruction. After surgery, the contraction latency difference was found to improve significantly (decrease) in patients who had a preexisting deficit. The mechanism for alteration in response time remains unclear, but an observed relationship between contraction latency and tibial translation supports a mechanical basis for the findings. It was concluded the sensorimotor changes associated with surgical reconstruction of the cruciate ligament may help to restore joint stability. The study highlights the need to appreciate sensorimotor consequences of cruciate ligament surgery.

After Partial Knee Replacement, Patients Can Kneel, But They Need to Be Taught to Do So: A Single-Blind Randomized Controlled Trial

Background and Purpose: Kneeling is an important functional activity frequently not performed after knee replacement, thus affecting a patients ability to carry out basic daily tasks. Despite no clinical reason preventing kneeling, many patients fail to resume this activity. The purpose of this study was to determine whether a single physical therapy intervention would improve patient-reported kneeling ability following partial knee replacement (PKR). Subjects: Sixty adults with medial compartment osteoarthritis, suitable for a PKR, participated. Methods: This was a single-blind, prospective randomized controlled trial. Six weeks after PKR, participants randomly received either kneeling advice and education or routine care where no specific kneeling advice was given. Reassessment was at 1 year postoperatively. The primary outcome measure was patient-reported kneeling ability, as assessed by question 7 of the Oxford Knee Score. Other factors associated with kneeling ability were recorded. These factors were scar position, numbness, range of flexion, involvement of other joints, and pain. Statistical analysis included nonparametric tests and binary logistic regression. Results: A significant improvement in patient-reported kneeling ability was found at 1 year postoperatively in those participants who received the kneeling intervention. Group allocation was the only factor determining an improvement in patient-reported kneeling ability at 1 year postoperatively. Discussion and Conclusion: The single factor that predicted patient-reported kneeling ability at 1 year postoperatively was the physical therapy kneeling intervention given at 6 weeks after PKR. The results of this study suggest that advice and instruction in kneeling should form part of a postoperative rehabilitation program after PKR. The results can be applied only to patients following PKR.

Valgus subsidence of the tibial component in cementless Oxford unicompartmental knee replacement

The cementless Oxford unicompartmental knee replacement has been demonstrated to have superior fixation on radiographs and a similar early complication rate compared with the cemented version. However, a small number of cases have come to our attention where, after an apparently successful procedure, the tibial component subsides into a valgus position with an increased posterior slope, before becoming well-fixed. We present the clinical and radiological findings of these six patients and describe their natural history and the likely causes. Two underwent revision in the early post-operative period, and in four the implant stabilised and became well-fixed radiologically with a good functional outcome. This situation appears to be avoidable by minor modifications to the operative technique, and it appears that it can be treated conservatively in most patients. Cite this article: Bone Joint J 2014;96-B:345–9.