Cementless AGC revision of unicompartmental knee arthroplasty

The clinical outcome of total knee arthroplasty is compromised by a previously implanted medial unicondylar knee arthroplasty

OBJECTIVE

To investigate the clinical outcome of patients that underwent conversion of a medial unicondylar knee arthroplasty (UKA) to a total knee arthroplasty (TKA) and to compare that outcome to patients that underwent primary TKA. It was hypothesized that those groups would significantly differ in terms of knee score outcome and implant survival.

METHODS

A retrospective-comparative study was conducted utilizing data from the Federal state's arthroplasty registry. Included were patients from our department that undergone a conversion of a medial UKA to a TKA (UKA-TKA group). The Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) from preoperative and 1-year postoperative was used. Moreover, the implant survival was analyzed.

RESULTS

In the UKA-TKA group, there were 51 cases (age 67 ± 10, 74% women), and in the TKA group, there were 2247 cases (age 69 ± 9, 66% women). The one-year postoperative WOMAC total score was 33 in the UKA-TKA group und 21 in the TKA group (p < 0.001). Similarly, the WOMAC pain, WOMAC stiffness, and WOMAC function scores were significantly worse in the UKA-TKA. After 5 years, the survival rates were 82% and 95% (p = 0.001). The 10-years prosthesis survival was 74% and 91% in the UKA-TKA and TKA groups, respectively (p < 0.001).

CONCLUSIONS

Based on our findings it is concluded that patients who received a TKA after UKA have inferior results than those that directly receive a TKA. This is true for both patient-reported knee outcome and prosthesis survival. Converting UKA to TKA should not be seen as an easy operation, but should rather be done by surgeons with considerable experience in both primary and revision knee arthroplasty.

Management of failed UKA to TKA: conventional versus robotic-assisted conversion technique

Background

Failure of unicompartmental knee arthroplasty (UKA) is a distressing and technically challenging complication. Conventional conversion techniques (CCT) with rods and jigs have produced varying results. A robotic-assisted conversion technique (RCT) is an unexplored, though possibly advantageous, alternative. We compare our reconstructive outcomes between conventional and robotic methods in the management of failed UKA.

Methods

Thirty-four patients with a failed UKA were retrospectively reviewed. Patients underwent conversion total knee arthroplasty (TKA) with either a CCT or RCT. Seventeen patients were included in each group. All procedures were done by a single surgeon at a single institution, with a mean time to follow-up of 3.6 years (range, 1 to 12). The primary outcome measures were the need for augments and polyethylene thickness. Secondary outcome measures were complications, need for revision, estimated blood loss (EBL), length of stay, and operative time.

Results

The mean polyethylene thickness was 12 mm (range, 9 to 15) in the CCT group and 10 mm (range, 9 to 14) in the RCT groups, with no statistical difference between the two groups (P = 0.07). A statistically significant difference, however, was present in the use of augments. In the CCT group, five out of 17 knees required augments, whereas none of the 17 knees in the RCT group required augments (P = 0.04). Procedurally, robotic-assisted surgery progressed uneventfully, even with metal artifact noted on the preoperative computerized tomography (CT) scans. Computer mapping of the residual bone surface after implant removal was a helpful guide in minimizing resection depth. No further revisions or reoperations were performed in either group.

Conclusions

Robotic-assisted conversion TKA is technically feasible and potentially advantageous. In the absence of normal anatomic landmarks to guide conventional methods, the preoperative CT scans were unexpectedly helpful in establishing mechanical alignment and resection depth. In this limited series, RCT does not seem to be inferior to CCT. Further investigation of outcomes is warranted.

Total Knee Arthroplasty After Failed Unicompartmental Knee Arthroplasty. Clinical Results, Radiologic Findings, and Technical Tips

BACKGROUND

The loss of anatomic references and bone stock turns unicompartmental knee arthroplasty (UKA) revision surgery difficult, and according to some authors, it is technically as challenging as a total knee arthroplasty (TKA) revision surgery.

METHODS

A retrospective review of 559 Oxford medial UKA was performed between 2007 and 2013. Nineteen knees were revised to TKA for reasons other than infection, most commonly for osteoarthritis progression.

RESULTS

The most frequent cause of failure in our series was osteoarthritis progression (10 cases, 52.63%). In 15 patients (78.95%), tibial stems were needed, and in 10 (55.5%), metallic blocks for augmentation of tibial plateau were used. Postoperative radiographic studies showed a correct implant alignment, preserving adequate joint line (24.8 mm), and patellar (1.1 mm) height (according to Insall-Salvati). After a mean follow-up of 21 months (range 6-51) mean values of 78.8 (standard deviation [SD] = 16.8) and 62.3 (SD = 19.6) were obtained for the physical and mental scores of the Knee Society Score test. In the SF-36 tests mean values of 45.2 (SD = 7.6) and 53 (SD = 5.2) were obtained for the physical and mental scores respectively. In one case, a varus/valgus instability occurred intraoperatively and it required revision with a prosthesis with higher constriction. No thromboembolic or infectious events were observed during postoperative follow-up.

CONCLUSION

Following a standardized technique, UKA revision surgery can be achieved with TKA in almost every case despite bone stock loss and lack of anatomic landmarks.

Revision of unicompartmental knee arthroplasty: implants used and causes of failure

Objective

to determine the causes of unicondylar knee arthroplasty failures, as well as identify the implants used and the need of bone grafting in patients undergoing revision UKA in Center of Knee Surgery at the Instituto Nacional de Traumatologia e Ortopedia (INTO) in the period between January 1990 and January 2013.

Methods

a retrospective analysis of the medical documentation and imaging, determining the cause of failure of UKA and the time of its occurrence, as well as prosthetic components implanted during the review and the need for bone grafting.

Results

in this study, 27 UKA failures in 26 patients were included. Collapse of one or more components was the main cause of failure, occurring in 33% of patients. Aseptic failure was identified in 30% of cases, progression of osteoarthrosis in 15%, infection and pain 7% each, and osteolysis and polyethylene failure in 4% each. Early failure occurred in 41% of all revisions of UKA and late failure in 59%. 23 patients have undergone revision of UK.

Conclusion

in 35% of revisions the use of bone grafting was needed in tibial area; in 3 cases we needed allograft from Tissue Bank. We did not use metal increase in any of the revision. In one patient we used implant constraint for instability.

Do bone loss and reconstruction procedures differ at revision of cemented unicompartmental knee prostheses according to the use of metal-back or all-polyethylene tibial component?

INTRODUCTION

Results of unicompartmental knee arthroplasty (UKA) revision are known but the severity of bone loss and the need for reconstruction are not detailed for different tibial implants.

HYPOTHESIS

Metal-backing UKA revision exposes the patient to more severe tibial bone loss and requires more substantial reconstruction procedures than cemented polyethylene UKA revision.

MATERIALS AND METHODS

This retrospective series of 23 revisions of UKA to total knee arthroplasty (TKA) compared 11 all-polyethylene UKAs with 12 metal-backing UKAs. Factors that contributed to failure were aseptic loosening (n=12) and osteoarthritis evolution (n=11). Both groups were similar regarding the demographic and clinical features. We reported bone loss and the reconstruction procedure to fill it according to the initially used tibial implant. The results were evaluated with the IKS score to a follow-up of 37 months (range, 24-67 months).

RESULTS

There were more tibial segmental bone loss (10 versus 3) and more metal wedges (8/12 versus 2/11) in metal-backing UKA revision (P<0.05). Tibial stems were more often used in metal-backing UKA revision (12/12 versus 7/11) (P=0.04). The results of TKA at follow-up did not differ according to whether the revised tibial implant was all polyethylene (IKS=155 [range, 107-195]) or metal-back (IKS=155 [range, 127-172]).

DISCUSSION

This study suggests that metal-backing UKA revision exposes the patient to more severe tibial bone loss requiring more substantial reconstruction. These results must be confirmed on a larger population, but surgeons should be alerted to this kind of revision surgery, which warrants having available a revision knee prothesis.

LEVEL OF EVIDENCE

Level III, case-control study.

Revision of unicondylar to total knee arthroplasty: a systematic review

Isolated unicompartmental osteoarthritis in the young patient is a difficult problem to treat; they may be too young to consider total knee arthroplasty due to difficulties with inevitable future revision. Unicompartmental knee arthroplasty is one possible solution as it is perceived by some as being a smaller surgical insult than total knee arthroplasty, with easier revision to total knee arthroplasty than a revision total knee arthroplasty. A total knee arthroplasty performed as a revision unicondylar knee arthroplasty is thought by some authors to have equivalent functional outcomes to a primary total knee replacement.

However, there have been several studies suggesting that revision is not as simple as suggested, and that function is not as good as primary total knee arthroplasty.

We performed a systematic review of the literature regarding outcomes after revision of a unicondylar knee arthroplasty.

Although there are many studies proposing selective use of the unicondylar knee arthroplasty, there are a number of studies highlighting difficulties with revision and poorer outcomes, and, therefore, the unicondylar knee arthroplasty cannot be considered a small procedure that will 'buy time' for the patient, and have results equal to a primary knee arthroplasty when revised. Further controlled studies, ideally randomised, are required before final conclusions can be drawn.

Validity of published outcome data concerning Anatomic Graduated Component total knee arthroplasty: a structured literature review including arthroplasty register data

PURPOSE

Total knee arthroplasty (TKA) as a treatment for end-stage osteoarthritis of the knee shows good results in terms of patient satisfaction. For the assessment of outcome and revision rate after total joint arthroplasty, there are two major data sources: clinical studies and national arthroplasty registers. The purpose of this study was to analyse the outcome of Anatomic Graduated Component (AGC) TKA reported in clinical studies and to perform a comparison with the outcome reported by national arthroplasty registers.

METHODS

A systematic literature review was performed using standardised methodology in order to determine the outcome and revision rate of AGC TKA. In a comprehensive meta-analysis of clinical studies and worldwide register results we examined the quality of the basic data and the occurrence and influence of potential bias factors. Confidence intervals were calculated to determine the statistical significance of differences.

RESULTS

We found significant differences as regards the revision rate measured in revisions per 100 observed component years. Compared to worldwide register data it turned out to be significantly lower in clinical studies published by the implant development team. Actually, they reported a revision rate of 0.18 revisions per 100 observed component years, whereas annual reports of national arthroplasty registers report 0.74 revisions per 100 observed component years. A comparison of the results from national arthroplasty registers of different countries revealed a significantly higher revision rate for Denmark in relation to worldwide register data.

CONCLUSIONS

A conventional meta-analysis of clinical studies is affected by the influence of the development team and therefore subject to bias. For the assessment of outcome arthroplasty register data should be rated as superior and, being used as reference data for the detection of potential bias factors in the clinical literature, could make an essential contribution to the quality of scientific meta-analysis.

Conversion of failed unicompartmental knee arthroplasty to TKA

As the number of unicompartmental knee arthroplasties performed continues to rise, so too will the number of failures. In order to justify its continued use, conversion to total knee arthroplasty must be evaluated. From 1993-2004, 22 consecutive knees from 18 patients with a failed unicondylar knee arthroplasty underwent conversion to total knee arthroplasty. The most common modes of failure were polyethylene wear (12 patients), loosening of the femoral (4 patients) or tibial component (3 patients), and osteoarthritis progression (3 patients). All patients were converted to primary cruciate retaining components. Twenty-seven percent of patients had contained defects on the femoral condyle that required bone graft. No femoral stems or metal augmentation were required. Forty-five percent of patients had contained defects on the tibia that required bone graft. Metal wedge augmentation was required in five knees (23%), and stems were used in two patients. Sixteen of 22 knees (73%) were followed for an average of 64.5 months. Knee Society knee scores and functional scores at latest followup were 93 and 78, respectively. Conversion of a failed unicondylar knee arthroplasty to a total knee arthroplasty is technically demanding, but may be done successfully with careful preoperative planning and possible need for revision techniques.

LEVEL OF EVIDENCE

Therapeutic study, level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

[Revision total knee arthroplasty after unicompartmental femorotibial prosthesis: 54 cases]

PURPOSE OF THE STUDY

We analyzed technical difficulties encountered when performing revision total knee arthroplasty in patients with unicompartmental femorotibial prostheses.

MATERIAL AND METHODS

This multicentric retrospective study included 54 revisions of unicompartmental femorotibial prosthesis with implantation of a total knee prosthesis. The series included 45 medial and nine lateral compartment prostheses. A gliding total knee prosthesis was implanted in 53 cases (98%) (39 standard, 14 revision). Mean time to failure of the unicompartmental prosthesis was four years. IKS scores were established at review. The radiological work-up included AP and lateral views in single leg stance and goniometry for 22 medial compartment revisions. Twenty-seven patients were seen for physical examination and x-rays and eight were lost to follow-up; data were recorded from medical files for 19 patients.

RESULTS

The revision procedure was considered easy in 82% of the cases. Mean follow-up after revision was four years (range 2 - 12 years). Subjective outcome was very satisfactory for 56% of the patients, satisfactory for 36% and unsatisfactory for 8%. The mean function score was 62 points, the mean knee score 85 points, and the mean flexion was 113 degrees. No laxity was found for 90% of the knees. The femorotibial angle was 180 +/- 2 degrees in 46% of the patients. The mechanical femoral angle was 90 degrees in 54% of the patients with 2-4 degrees varus in 42%. The mechanical tibial angle was 90 degrees in 46% of the patients with 2-8 degrees valgus in 37%. Complications included pulmonary embolism (n=2), mobilization under general anesthesia (n=3), arthrolysis (n=1), lateral vertical patellectomy (n=1), and secondary infection (n=1). There were five failures requiring changing the total knee prosthesis.

DISCUSSION

Loss of bone stock raises specific problems during revision of unicompartmental knee prostheses. Loss of tibial bone is more frequent but it is more difficult to correct for loss of femoral bone. A gliding knee prosthesis is generally preferred for first intention revision. We recommend a long stem when the bone defect is important or involves loss of cortical bone. We have had good mid-term results with revision total knee prostheses after unicompartmental prostheses. Longer follow-up is needed. Poor results were obtained when revision was performed for persistent pain without a clearly defined cause. The presence or not of significant bone loss did not appear to affect outcome. The observation of medial laxity in case of failed lateral unicompartmental prostheses suggests a more constrained total knee prosthesis might be indicated. Compared with earlier series, our results with total knee prostheses after unicompartmental prostheses appear to be better than after tibial valgus osteotomy and also better than after total knee arthroplasty. Conversely, they would be less satisfactory than for primary total knee arthroplasty. The surgical procedure for revision total knee arthroplasty after unicompartmental prosthesis requires precision and skill but is not technically difficult.

Survivorship of AGC knee replacement in juvenile chronic arthritis: 13-year follow-up of 77 knees

This study analyzed the survivorship and results of 77 knee replacements in 52 patients with juvenile chronic arthritis using the nonconstrained Anatomically Graduated Components (AGC; Biomet, Warsaw, IN) prosthesis design. Patients were operated on between the years 1985 and 1995. The mean duration of the general disease was 24 years (range, 10-56 years), and the mean age of the patients at the time of surgery was 33 years (range, 16-64 years). Bone-grafts were installed into 15 knees, custom-made components were used in 5 knees, and cemented fixation in 4 knees. The patella was resurfaced in 23 knees. Clinical follow-up examinations were conducted 3 months, 1 year, 4 years, and 8 years postoperatively. An interview was arranged at the end of 1998, 3 to 13 years after surgery; 2 patients were not reached, and 2 died during the follow-up. Fifty-five of 73 (75%) knees were subjectively excellent, 18 (25%) were fair, and none was poor. Radiolucent lines of 1.0 to 1.5 mm were found under 14 tibial trays but not adjacent to femoral components. No deep infections were detected. One knee was revised 4 years after the implantation. The overall survival was 99% (95% confidence interval, 92-100) at 5 years. We consider these results excellent in this demanding patient material. The nonconstrained AGC prosthesis with cementless fixation proved to be feasible in knee replacement in patients with juvenile chronic arthritis.