Study reference

Study characteristics

Patient characteristics ²

Intervention (I)

Comparison / control (C) ³

Follow-up

Outcome measures and effect size ⁴

Comments

Christensen, 2013

Type of study: retrospective chart review

Setting: hospital

Country: Denmark

Source of funding: unknown

Inclusion criteria: patients undergoing cementless primary THA from August to November 2009 at Hørsholm Hospital, Orthopaedic Hip Clinic

Exclusion criteria: major per- or post-operative complications such as fracture, deep infection, or dislocation and cases requiring bone transplantation were excluded. Patients having complaints that led to early referral and additional outpatient follow-up outside of the planned three- and 12-month follow-up visits were also excluded.

N total at baseline:

N=249

Important prognostic factors²:

Age ± SD: 68 (26 to 93)

Sex:

36 % M

Main indication was osteoarthritis (OA) (n = 215; 91%). Other indications were dysplasia (n = 10; 4%), sequelae from fracture (n = 6; 2.5%), rheumatoid arthritis (n = 4; 1.7%) and caput necrosis (n = 1; 0.4%).

Describe intervention (treatment/procedure/test):

Radiographic follow-up

Describe control (treatment/procedure/test):

-

Length of follow-up:

3 and 12 months

Loss-to-follow-up:

A total of 11 patients were excluded before the three month follow-up visit; seven patients had fractures, four of which occurred during surgery. The remaining four patients had major post-operative complications requiring revision; two had loosening of the cup and two had deep infection.

One patient had fallen between the two outpatient visits and had suffered a trochanteric fracture and was thus excluded at the 12-month follow-up.

Outcome measures and effect size (include 95%CI and p-value if available):

Among 417 outpatient visits, the radiographic examination had direct consequence in five cases (1.2%;95% confidence interval (CI): 0.4 to 2.8%); however, in only two cases (0.48%; 95% CI: 0.06 to 1.72) did the radiographs result in consequences other than increased follow-up.

Röder (2003)

Type of study:

Analysis of follow-up data

Setting:

Data were derived from the database of the Maurice E. Müller Institute for Evaluative Research in Orthopaedic Surgery. Data were collectd between 1967 and 2002 from 41 hospitals.

Country:

Several European countries

Source of funding:

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

Inclusion criteria:

- osteoarthritis as the main diagnosis, primary THA, age over 20 years at THA, and the availability of serial documented follow-up examinations for at least ten years after operation with a complete set of preoperative, immediately postoperatieve and follow-up radiographs.

Exclusion criteria:

-

N total at baseline: the database search identified 15743 patiens

Important prognostic factors²:

Age ± SD:

The median age at surgery was 67.4 years with a 75% percentile of 73.8 years and a 25% percentile of 60.1 years.

Sex:

50,4% male

49,6% female

Describe intervention (treatment/procedure/test):

Total hip arthroplasty

Describe control (treatment/procedure/test):

-

Length of follow-up:

Patients with a follow-up of at least 20 years were selected.

Loss-to-follow-up:

-

Outcome measures and effect size (include 95%CI and p-value if available):

Sensitivity and specificity:
Sensitivities ranged between

0.00 and 0.49 for uncemented and between 0.00 and 0.6 for

cemented cups. Figure 2 and Tables V and VI give the mean

values. A slight time-dependent increase in sensitivity was

seen during the first decade after operation. The specificity

of all indices was constantly between 0.89 and 1.00, regardless

of the mode of fixation of the cup. Figure 3 gives the

mean values. Time trends of specificity were slightly negative

and, unlike sensitivity, the specificities of the various

clinical indices appeared to be homogenous.

For the stems, sensitivities ranged between 0.0 and 0.57

for cemented and between 0.0 and 0.46 for uncemented

components. The sensitivities of most variables showed

more constant time trends compared with those of the cups.

Figure 2 and Tables VII and VIII give the mean values. Most

values in the uncemented group had a higher variability over

time within the mentioned range. The specificity of all

indices was constantly between 0.9 and 1.0 for both types of

fixation. Time trends of specificity were also slightly negative

and homogenous, compared with the sensitivities.

Figure 3 gives the mean values. The variability of values

with time was again higher in the uncemented group.

Predictive values
With regard to loosening of the cup some

types of pain were rarely diagnosed and therefore predictive

values could not be calculated in all cases. PPVs increased

during the first decade after operation from 0.00 to 0.66.

The time-dependent variation was similar for both cemented

and uncemented cups (Fig 4, Tables V and VI). NPVs

decreased over time from 1.00 to 0.86. This decrease was

relatively constant for uncemented cups whereas for

cemented cups a relatively sharp decrease in NPV was

observed at six years after operation (Fig. 5, Tables V and

VI).

The calculated NPVs for loosening of the stem from one

to ten years were constantly above 0.87 regardless of the

year of follow-up and type of fixation of the stem. For both

methods of fixation, the NPV at four years after operation

was higher than at eight years (Fig. 5, Tables VI and VIII). PPVs varied considerably, especially in the uncemented

group, and were rarely higher than 0.5 with a slight constant

upward trend with time (Fig. 4, Tables VI and VIII).

King (2004)

Type of study:

Retrospective review of records

Setting:

Hospital based

Country:

Boston, Massachusetts, United States

Source of funding:

The authors did not receive grants or outside funding in support of their

research or preparation of this manuscript. One or more of the authors

received payments or other benefits or a commitment or agreement to

provide such benefits from a commercial entity (DePuy, a Johnson and

Johnson Company). No commercial entity paid or directed, or agreed to

pay or direct, any benefits to any research fund, foundation, educational

institution, or other charitable or nonprofit organization with which the

authors are affiliated or associated.

Inclusion criteria:

Retrospectively reviewed the records of 161 patients with a total of 200 consecutive toal knee replacements perfomed between April 1996 and July 1997 by the same surgeon with the same prosthesis (PFC Sigma; DePuy, Warsaw, Indiana).

All of the operations were performed at one of two hospitals,

and all follow-up examinations were conducted at the same

office. For the purposes of this study, we defined patients as

not having returned for follow-up if they had had no contact

of any type with their surgeon beyond six months after the

date of the surgery.

Exclusion criteria: -

N total at baseline: 161 patients

Important prognostic factors²:

Age ± SD:

Control: mean age at time of surgery was 71.3 years (range 44 to 83)
Intervention: mean age at the time of surgery was 68.1 years (range 40 to 84)

Sex:

Control: nine (30%) of the patients were male

Intervention: 54 (30%) were male

Weight:

Control: mean weight at time of surgery was 82.0 kg (range 52 to 11)

Intervention: mean weight 79.0 kg (range 30 to 130)

No significant differences in baseline sex, diagnosis, deformity (varus or valgus), or weight.

The patients who had not attended

follow-up appointments tended to be older at the time

of the surgery than those who had attended follow-up appointments and more of them had died

Describe intervention (treatment/procedure/test):

Returned for follow-up after total knee arthroplasty

Patients who had been returning for follow-up appointments

were evaluated in the same fashion. If the patient had

already returned for a follow-up appointment at a minimum

of five years, the Knee Society pain and function scores were

determined from the chart. If the patient had been keeping

follow-up appointments but had not yet returned for the fiveyear

evaluation, he or she was contacted by one of the authors, who administered the pain and function components

of the Knee Society Clinical Rating System in a telephone

interview. The scores were compared with the preoperative

values recorded in the chart. All patients who had not yet returned

for a clinical evaluation at a minimum of five years

were asked to return for clinical and radiograph examination. When a patient had been keeping the prescribed follow-up appointments but had not yet returned for the five-year followup evaluation and could not be contacted with use of the last known contact information in the chart, an attempt was made

to locate that patient with use of the standardized Internet search algorithm employed for the patients who had not returned

for follow-up.

Describe control (treatment/procedure/test):

Not returned for follow-up

after total knee arthroplasty

Patients who had not returned for follow-up were evaluated by one of the authors (A.S.M.), who had not been involved in their care. The evaluation was carried out by means of a telephone interview, during which the patients were asked

about the status of the knee prosthesis, the reason that they did not return for follow-up, and whether a different surgeon had been evaluating or treating the knee. A patient who gave more than one reason for not adhering to the recommended follow-up regimen was asked to identify which reason he or she considered to be primary. Scores for the pain and function

components of the Knee Society Clinical Rating System were

determined on the basis of this telephone interview and were

compared with the preoperative values recorded in the patient’s chart. Patients were educated about the importance of the recommended follow-up regimen. All patients were asked to schedule an appointment for complete physical examination

and radiographs.

Length of follow-up:

The minimum duration of follow-up was five years (mean, 64.0 months; range, sixty to secenty-three months).

Loss-to-follow-up:

Control group: seven patients (8 knees) had died of unrelated causes.

Intervention group: ten patients (11 knees) had died of unrelated causes

Outcome measures and effect size (include 95%CI and p-value if available):

None of the patients who had not returned for follow-up

had required additional surgery on the knee; six patients who

had returned for a follow-up evaluation at a minimum of five

years had required additional surgery on the knee. This difference

was not significant. The reasons for additional surgery included

late infection (two patients), arthroscopic manipulation

(two), synovectomy with exchange of the polyethylene liner because

of recurrent varus deformity (one), and excision of a lateral

joint line cyst (one).

Both the patients who had returned

for follow-up and those who had not had a significant

improvement in the postoperative scores for the pain and

function components of the Knee Society Clinical Rating System

compared with the preoperative values (p <0.0001).

There was no significant difference in the pain and function

scores at a minimum of five years between the patients who

had and those who had not attended follow-up appointments.

Two patients who had not returned for follow-up appointments and four who had returned reported that they were dissatisfied with the knee replacement (p = 0.25). Of the two dissatisfied patients who had not returned for follow-up appointments, one had bilateral osteoarthritis of the knee and complained of a limb-length discrepancy following correction of a large varus deformity in one of the knees. The other patient complained of residual stiffness one month after the surgery and did not return for follow-up again.

An attempt was made to locate patients who had not returned

for follow-up at a minimum of five years by using their

last known contact information or the last known information

on their next of kin. When a patient could not be located with

use of this information, a series of searches of free, readily available

Internet databases was carried out with use of the patient’s

most recent demographic information as a starting point (see article).

Study reference

(first author, year of publication)

Bias due to a non-representative or ill-defined sample of patients?¹

(unlikely/likely/unclear)

Bias due to insufficiently long, or incomplete follow-up, or differences in follow-up between treatment groups?²

(unlikely/likely/unclear)

Bias due to ill-defined or inadequately measured outcome ?³

(unlikely/likely/unclear)

Bias due to inadequate adjustment for all important prognostic factors?⁴

(unlikely/likely/unclear)

Christensen (2013)

Unlikely (all THA patients Aug-Nov 2009)

Likely (follow-up too short)

Unclear

Unclear

Röder (2003)

Not applicable

Unclear

Unlikely

Likely (only age and gender)

King (2004)

Unclear (It is written in the study that total knee replacements performed between 1996 and July 1997 by the same surgeon with the same prosthesis were selected. However, it is not stated if a preselection is made of all the knee replacements performed by the surgeon)

Unclear (it is unclear if the reasons for (not) returning to the follow-up appointments differ between the two groups)

Likely (outcome assessors were not blinded)

Likely (no multivariate statisitical analysis done)