Sage Journals: Discover world-class research

Abstract

Background and Aims:

Alterations in periprosthetic bone are common sequlae of prosthetic implants. This prospective 3-year study was performed to follow regional periprosthetic bone turnover after uncomplicated total hip arthroplasty (THA) using single-photon emission computed tomography (SPECT).

Material and Methods:

Eighteen patients (nine men, nine women: mean age 61 years, range from 50 to 73 years) with primary hip osteoarthritis underwent either uncemented or cemented THA. The SPECT measurements were taken 6, 12, and 36 months after THA. B one mineral density (BMD) measurements were performed on the patients during follow-up.

Results:

The mean SPECT uptake ratios decreased significantly in the regions of interest (ROIs) during follow-up compared to baseline value, in the trochanter major (p = 0.006), the trochanter minor (p = 0.009) and the total area (p = 0.018). Despite these decreases the uptake ratios in the medial cortex (p = 0.014), tip (p = 0.002) and total area (p = 0.016) remained significantly higher in the operated side than in the contralateral side (non-operated) 3 years after THA. Changes in bone turnover in the vicinity of the implant did not correlate with changes in periprosthetic BMD.

Conclusions:

Local periprosthetic bone turnover decreased slowly after THA and did not recover to the level typical of non-operated hips. This led us to suggest that bone turnover around the femoral implants remains increased more than 3 years after THA even if there are no signs of failure of the prosthesis.

Keywords

Total hip arthroplasty single-photon emission computed tomography bone turnover bone mineral density periprosthetic bone dual-energy X-ray absorptiometry

INTRODUCTION

Total hip arthroplasty (THA) is a common operation in patients with osteoarthritis of the hip (1). The insertion of metallic implant causes changes in bone mass and bone turnover in the vicinity of the implant. This is usually seen as a resorption of bone in the proximal part of femur because of altered loading patterns (stress shielding) (2, 3). Orthopedic surgeons are interested in following periprosthetic bone reactions in order to evaluate the results of THA and to discover whether some prostheses are more preferable than others. Several methods have been used to follow periprosthetic bone changes, such as serial standard radiographs, computed tomography, magnetic resonance imaging, and dual-energy X-ray absorptiometry (DXA) to follow periprosthetic bone changes (4–7).

Single photon emission computed tomography (SPECT) bone scanning using Tc-99m-diphosphonates is a useful method for detecting disorders of the skeleton and for measuring bone turnover (8–10). A few studies discussed the role of SPECT after arthroplasty. McMahon et al. studied femoral head vascularity after hip resurfacing and Soininvaara et al. studied bone turnover after uncomplicated total knee arthroplasty (TKA) (11, 12).

This prospective 3-year study aimed to follow regional periprosthetic bone turnover after uncomplicated THA with SPECT. The main purpose of the study was to examine whether or not bone turnover recovers to its ‘normal’ level after successful arthroplasty.

Furthermore, we studied correlations between periprosthetic SPECT uptake and changes in periprosthetic bone mineral density (BMD).

MATERIALS AND METHODS

PATIENTS

Eighteen patients with primary hip osteoarthritis were included in this prospective periprosthetic SPECT study. Patients (nine men and nine women) underwent either uncemented or cemented primary THA at Kuopio University Hospital from November 1993 to August 1994 using standard operative techniques. In order to be included in this study, the patients were required to be without any bone metabolic disease and to not have taken any bone-affecting drugs previously or during the follow-up. All patients provided written informed consent. The study protocol was approved by the local Ethics Committee (13).

The SPECT measurements were taken 6, 12, and 36 months after THA, and BMD measurements were taken within 2 weeks postoperatively, and at 3, 6, 12, 24, and 36 months after THA. Regular clinical and radiological follow-ups were organized. A modified Harris Hip Score (mHHS) was used (maximum 80 points) to evaluate clinical outcomes (14).

The femoral prostheses used in this study were uncemented Bimetric Titanium Alloy (Ti6A14V) implants (n = 9, Biomet Inc., Warsaw, IN, USA), uncemented PCA E Series Hip System (n = 5, Howmedica International Divisions of Pfizer), and cemented Lubinus SPII stems with collar (n = 4, Waldemar Link CMBH&CD, Germany). Uncemented femoral stems are proximal load carrying components, but they have some differiencies. PCA E Serie femoral stem is made from cobolt-chromium, the shape of the stem is anatomic and the surface is double layer porouscoated. The Bimetric stem is made from titanium alloy, it is straight and the surface of the stem is plasmasprayed. The bone cement used was Palacos® R-40 cum Gentamicin (contrast medium zirconium, Schering-Plough, Brussels, Belgium).

The mean age of the patients was 61 years (50–73 years). Their mean body mass index (BMI) was 30.3 kg/m² (20.8–40.6 kg/m²) (Table 1). The normal postoperative mobilization schedule was followed, where patients with cemented arthroplasty were encouraged to perform full weight-bearing exercises immediately after the operation. Patients with uncemented prostheses were encouraged to perform partial-weight bearing exercises with crutches on the operated hip for 6 weeks after THA. In two patients, postoperative X-rays showed fissure fractures in the operated femur after uncemented arthroplasty, but these healed without any later complications.

TABLE 1

Characteristics of the study subjects.

Number of patients	n = 18 (9 men; 9 women)

Age (years)	61 (50–73)
BMI* (kg/m²)	30.3 (20.8–40.6)
Type of prosthesis
– uncemented
– Biomet	n = 9
– PCA	n = 5
– cemented
– Lubinus	n = 4
Modified Harris Hip Score (max. 80 points)
– preoperative	42 (19–60)
– 1 year after THA§	75 (64–80)
– 2 year after THA	76 (58–80)
– 3 year after THA	76 (55–80)

body mass index

total hip arthroplasty

SPECT

The SPECT scans were performed using a three-headed SPECT system (Siemens MultiSpect 3, Siemens Gammasonics Inc., Des Plaines, IL, USA) equipped with high-resolution collimators. The measurements were started 4 h after an intravenous injection of 740 MBq of Tc-99m-methylene diphosphonate (Tc-99m-MDP, Medronate II®, Amersham, Bucks., UK). A full 360° rotation was acquired (40 views/head, each for 35 s, using a 128 × 128 matrix).

After reconstruction using a filtered back-projection technique (Butterworth filter: order 6 and cut-off frequency 0.5 / cm), the data were carefully aligned in transverse, coronal, and sagittal projections in order to view both femurs and acetabular areas in the same plane. Thereafter, four original slices were summed to the final 14-mm-thick coronal slices that were used in quantification. Twelve symmetrical regions of interest (ROIs) (trochanter major, trochanter minor, lateral cortex, medial cortex, tip and reference area above the acetabulum) were manually drawn (lower threshold 7–9%) on the prosthesis and contralateral sides (Fig. 1). All regional uptake values (in counts/voxel) were divided by the averages obtained from the sum of reference areas to give regional uptake ratios. In addition, a total average uptake ratio (total area) was calculated over the femoral ROI in the ipsi- and contralateral sides (Table 2).

TABLE 2

The mean SPECT uptake ratios (sd) in the regions of interest around the femoral stem during the 3-year follow-up.

	Prosthesis side (n = 18)			Contralateral side (n = 18)

Region	6 months	1 year	3 years	6 months	1 year	3 years
Trochanter major	2.56 (1.13)	2.07 (0.92)	1.36 (0.50)**	1.17 (0.54)	1.17 (0.43)	1.15 (0.34)
Trochanter minor	2.16 (1.02)	1.60 (0.70)	1.13 (0.35)**	1.15 (0.44)	1.35 (0.53)	1.28 (0.37)
Lateral cortex	1.66 (0.77)	1.34 (0.57)	1.02 (0.36)	0.97 (0.42)	1.01 (0.42)	0.89 (0.27)
Medial cortex	1.74 (0.77)	1.28 (0.45)	0.97 (0.30)	0.86 (0.30)	0.93 (0.41)	0.83 (0.30)
Tip	2.26 (0.99)	1.60 (0.63)*	1.25 (0.41)	0.87 (0.28)	0.91 (0.43)	0.86 (0.36)
Total area	2.08 (0.87)	1.58 (0.55)*	1.14 (0.32)*	1.00 (0.36)	1.07 (0.38)	1.00 (0.28)

All ratios were count/voxel normalized to a reference area taken above the acetabulum. Significant changes in SPECT ratio compares to the 6-month postoperative ratio;

p < 0.05,

p < 0.01 (Wilcoxon test). Bonferroni correction was performed.

Fig. 1.

A SPECT image showing the twelve ROIs; a prosthesis side (right femur) and a control side (left femur).

DXA

The BMD measurements were taken using DXA (Lunar DPX; Lunar Co., Madison, WI, USA) with special orthopedic software (Lunar; version 1.2) according to the ROIs of Gruen and Lunar (15). The technique is reported in more detail in previously published articles both cemented and uncemented prostheses (7, 14).

Because the one purpose of the study was to compare results of SPECT and BMD measurements, five ROIs similar to those used in the SPECT measurements were created when the BMD values were calculated. Gruen ROIs 2 and 3 were combined in order to create the lateral cortex ROI and ROIs 5 and 6 were combined for the medial cortex ROI. The Gruen ROI 4 was same as the tip ROI. Lunar ROIs A and B were combined to form the trochanter major ROI and Lunar ROIs C and D formed the trochanter minor ROI. All five ROIs were combined to give the total area (Table 3).

TABLE 3

The mean bone mineral density (g/cm²) (sd) in the different regions of interest during the 3-year follow-up.

Region	Postoperative (n = 18)	3 months (n = 18)	6 months (n = 18)	1 year (n = 18)	2 years (n = 18)	3 years (n = 18)
Trochanter major	1.05 (0.22)	0.94 (0.23)**	0.92 (0.27)	0.90 (0.29)	0.92 (0.29)	0.90 (0.31)
Trochanter minor	1.34 (0.27)	1.09 (0.25)***	1.08 (0.26)	1.02 (0.29)	1.02 (0.26)	1.00 (0.32)
Lateral Cortex	1.85 (0.28)	1.72 (0.36)**	1.69 (0.36)	1.71 (0.36)	1.70 (0.40)	1.69 (0.39)
Medial cortex	1.70 (0.25)	1.57 (0.31)***	1.57 (0.30)	1.57 (0.33)	1.55 (0.32)	1.56 (0.35)
Tip	1.83 (0.27)	1.74 (0.29)*	1.74 (0.28)	1.74 (0.28)	1.76 (0.31)	1.74 (0.30)
Total area	1.56 (0.23)	1.41 (0.27)***	1.40 (0.27)	1.39 (0.29)	1.39 (0.28)	1.38 (0.30)

Significant change in BMD compared to the immediate postoperative value;

p < 0.05,

p < 0.01,

***

p < 0.001 (Wilcoxon test). Bonferroni correction was performed.

STATISTICAL ANALYSIS

SPSS software version 11.0 (SPSS Inc., Chicago, IL, USA) was used for the statistical analyses. The non-parametric statistical tests used were the Mann-Whitney test, the Wilcoxon test and Spearman's correlation. Statistical significance was defined as p < 0.05. The SPECT uptake ratios and BMD values were expressed as means and standard deviations (SD). Postoperative changes in the SPECT uptake ratios and BMD values were calculated using the first measured SPECT uptake ratio/BMD value as a reference: this SPECT uptake ratio/BMD value was compared to subsequent SPECT uptake ratios/BMD values in each ROI. The differences were expressed as percentages.

RESULTS

At the end of the follow-up there were no signs of loosening or other complications after THA. The mHHS changed from the average preoperative value of 42 to 75, 76, and 76 at 12, 24, and 36 months after the operation, respectively.

The mean SPECT uptake ratios (SD) and changes up to 3 years in the ROIs are shown in Table 2. The mean SPECT uptake ratios decreased in all ROIs from that of baseline values (six months after THA). The changes were significant at one year in the tip and total area (p < 0.05), and at three year in the trochanter minor (p < 0.01), trochanter major (p < 0.01) and total area (p < 0.05). Despite this decrease the uptake ratios in the medial cortex (p = 0.014), tip (p = 0.002) and total area (p = 0.016) remained significantly higher in the operated side than in the contralateral side (non-operated) at three years after THA. The uptake ratio in the trochanter minor uptake ratio was lower in the operated side (p = 0.034) (Fig. 3).

Fig. 2.

DXA images showing Gruen ROIs (A) and Lunar ROIs (B).

Fig. 3.

The mean SPECT uptake ratio (with the range of uptake ratios) in the prosthesis and control sides measured 3 year after THA. Grey bars represent uptake ratios in the prosthesis side and white bars represent uptake ratios in the control side. Significant differences between the sides were analysed using the Wilcoxon test (p < 0.05).

The mean BMD values (SD) and percentage changes are shown in Table 3 and Fig. 4. The BMD decreased by 5% to 19% in all ROIs during the first 3 months. All of these changes were statistically significant (p < 0.05 to p < 0.001). Following this, a slow decrease in BMD continued in the proximal part of femur, reaching −26% in the trochanter minor by the end of the follow-up. Only minimal BMD changes were found in the other ROIs after 3 months.

Fig. 4.

The mean change (%) in BMD in the five regions of interest and the total area.

No significant correlations were found between yhe SPECT uptake ratio and changes in BMD. Three different types of prostheses were implanted. The rate of bone turnover in the uncemented stems (n = 14) was lower than that in the cemented stems (n = 4) by the end of follow-up (Fig. 5).

Fig. 5 a, b.

Changes in total average SPECT uptake ratios compared to the type of prosthesis over 6–12 months (A) and 6–36 months (B) of follow-up. The black circle represents the revision case.

DISCUSSION

In this prospective three-year study, 18 patients were followed with high-resolution SPECT in order to examine periprosthetic bone turnover around the femoral stem. We found that local bone turnover in the vicinity of the implant decreased slowly during the 3 years of follow-up. This decrease was statistically significant in the trochanter major, trochanter minor, and the total area by the end of follow-up. We also compared bone turnover rates in the operated hip and the contralateral hip (non-operated) at the end of follow-up. The SPECT uptake ratios remained higher in the operated hip except in one ROI (the trochanter minor). The bone turnover rate did not return to the level that seems to be typical of non-operated hips. During the 3-year follow-up, no signs of aseptic loosening or periprosthetic infection were observed in any of the patients. Thus, it seems that the normal phenomenon after THA is a decrease in bone turnover around the femoral stem, although still being higher than that found in normal bone, even if there are no signs of failure of the prosthesis.

Rahmy et al. studied 80 asymptomatic patients to establish the course and duration of bony ingrowths after uncemented hydroxyapatite-coated arthroplasty using a quantitative analysis of Tc-99m-MDP uptake. They found decreased bone turnover 1 year after THA, but this remained higher than the normal level. They concluded that this is normal shortly after THA. They also suggested that this ‘normal’ database could be used as a reference point to detect failures of THA (16). Utz et al. performed a 3-year prospective study with 97 patients to determine the natural postoperative appearance of bone scans using Tc-99m-MDP. They used a four-point grading system to classify patients according to the rate of bone turnover after THA and found that about 20% of patients have increased bone activity for more than 1 year, and 10% have a persistent increase in bone turnover after THA (17). Increased SPECT uptake indicating normal post-operative remodelling was also found 2 years after uncomplicated TKA in one study (12). The results of our study are in agreement with these findings.

Interestingly, we found that two patients had a high rate of bone turnover in the total area 3 years after THA (Fig. 5b). In the patient who underwent uncemented THA a markedly elevated SPECT uptake was found in the lateral cortex and the tip of the prosthesis. At that time, the patient was asymptomatic and X-rays showed no signs of loosening. However, 5 years after the operation, the patient suffered from thigh pain and new X-rays showed osteolytic lesions in the lateral side of the stem. The patient underwent a revision operation 6 years after primary THA because of aseptic loosening of the implant. In agreement with Utz et al. (17), we suggest, that a persistent increased SPECT uptake ratio may be a sign of aseptic loosening. It is thus prudent to follow patients with persistent increases in bone turnover rate around their prosthesis more carefully because this may be an early sign of arthroplasty failure.

There may be some other factors influencing the rates of bone turnover after THA. Rosenthall et al. studied the bone turnover rate for 12 months after THA where two different types of implants were used. In their study, the patients either received a titanium alloy S-ROM prosthesis or a cobalt-chrome alloy AML prosthesis (the elastic modulus of the S-ROM prosthesis is half that of the AMLprosthesis). They found significant differences in bone turnover in most of the ROIs between these two types of implants, with different levels of stiffness (18). Oswald et al. followed 21 patients with uncomplicated porous-coated THA for 2 years. In their prospective three-phase bone scan study, they concluded that the pattern of bone turnover differs in patients with uncemented THA from that seen in patients with cemented THA (19). In this study, three types of prostheses were implanted and two different fixation methods were used. Each type of prosthesis was associated with a different pattern of bone turnover, and bone turnover was lower around uncemented stems compared with cemented stems (Fig. 5b). Our study confirms that each implant seems to have own pattern of regional bone turnover after THA. This should be recognised when interpreting clinical patients. It is unlikely that different postoperative mobilisation schedule has influenced regional bone turnover three years after operation.

Several prospective BMD studies have shown that most bone loss occurs during the first 3–6 months after THA, and that by 1 year after the operation only minimal changes in BMD are found (7, 12, 20–22). A similar behavioral pattern of BMD was found in the study. Previously, we found that elevated SPECT uptake was related to early periprosthetic bone loss. In this study, SPECT uptake was compared with BMD changes during the period when maximal bone resorption usually occurs (the first 6 months after THA) (13). In the present study, SPECT uptake was compared with later BMD changes when the changes in bone density were only minimal, and no correlations were found. This is in agreement with results of Rosenthall, who suggested that the degree of radio-phosphate deposition is a reflection of bone turnover, but this may not correlate with BMD changes after THA (23).

Interestingly, the trochanter minor ROI uptake ratio was lower in the operated side than in the control side at the end of 3-year follow-up. The trochanter minor ROI is the smallest and more susceptible to measurement error which may explain the result.

This study had some limitations. For example, we did not measure the immediate postoperative bone turnover rate but only the rate 6 months after THA: also, the sample size was quite small, with different implants. Manual localization and drawing of the ROIs in SPECT analyses is not as accurate as localization of the ROIs in DXA analyses. However, we believe that reactions in proximal femoral bone are highly visible 6 months after THA.

The present study showed that SPECT is a feasible method for following periprosthetic bone turnover after THA. The local periprosthetic bone turnover rate decreased slowly after THA and did not recover to the level typical of non-operated hips. This led us to suggest that bone turnover around femoral implants remains increased for more than 3 years after THA, even if there are no signs of failure of the prosthesis. This should be noted in clinical practise when analyzing SPECT examinations. Although SPECT method is not suitable for routine THA follow-up, patients with persistent symptoms after uncomplicated arthroplasty may benefit from it. Larger prospective studies with preoperative baseline measurements, different stem designs and longer follow-up are warranted.

Footnotes

ACKNOWLEDGEMENTS

The authors thank Riitta Toroi, R.N. and Eila Koski, R.N., for their expert technical assistance.

References

Harris

Sledge

: Total hip and total knee replacement. N Engl J Med. 1990; 323: 725–731.

Bobyn

Mortimer

Glassman

: Producing and avoiding stress shielding: Laboratory and clinical observations of noncemented total hip arthroplasty. Clin Orthop 1992; 274: 79–96.

Huiskes

Weinans

van Rietbergen

: The relationship between stress shielding and bone resorption around total hip stems and effects of flexible materials. Clin Orthop 1992; 274: 124–134.

Engh

Massin

Suthers

: Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop 1990; 257: 107–128.

Johnston

Fitzgerald

Jr. Harris

: Clinical and radiological evaluation of total hip replacement. A standard system of terminology for reporting results. J Bone Joint Surg. 1990; 72-A: 161–168.

Kilgus

Shimaoka

Tipton

: Dual-energy X-ray absorptiometry measurement of bone mineral density around porous-coated cementless femoral implants. J Bone Joint Surg. 1993; 75-B: 279–287.

Venesmaa

Kröger

HPJ

Miettinen

HJA

: Monitoring of periprosthetic BMD after uncemented total hip arthroplasty with dual-energy X-ray absorptiometry- a three-year follow-up study. J Bone Miner Res. 2001; 6: 1056–1061.

Collier

Jr. Krasnow

Hellman

: SPECT bone scanning. In: Collier

Jr. Fogelman

Rosenthall

. Skeletal nuclear medicine St. Louis, MI, USA; 1996: 45–70.

Israel

Gips

Hardoff

: Bone loss in patients with chronic renal disease: Prediction with quantitative bone scintigraphy with SPECT. Radiology 1995; 196: 643–646.

10.

Collier

Carrera

Johnson

: Detection of femoral head avascular necrosis in adults by SPECT. J Nucl Med. 1985; 26: 979–987.

11.

McMahon

Young

Ballok

: Vascularity of the femoral head after Birmingham hip resurfacing. A Technetium Tc 99m bone scan/single photon emission computed tomography study. J Arthroplasty 2006; 4: 14–21.

12.

Soinivaara

Nikola

Vanninen

: Bone mineral density and single photon emission computed tomography changes after total knee arthroplasty: a 2-year follow-up study. Clin Physiol Funct Imaging 2008; 2: 101–106.

13.

Kröger

Vanninen

Overmyer

: Periprosthetic bone loss and regional bone turnover in uncemented total hip arthroplasty: A prospective study using high resolution single photon emission tomography and dual-energy X-ray absorptiometry. J Bone Miner Res. 1997; 3: 487–492.

14.

Venesmaa

Kröger

HPJ

Miettinen

HJA

: Periprosthetic bone loss after cemented total hip arthroplasty. A prospective 5-year dual-energy X-ray absorptiometry study. Acta Orthop Scand 2003; 1: 31–36.

15.

Gruen

McNeise

Amstutz

: “Modes of failure” of cemented stem-type femoral components. A radiographic analysis of loosening. Clin Orthop 1979; 141: 17–27.

16.

Rahmy

AIA

Alfons

Tan

: Quantitative analysis of technetium-99m-methylene diphosphonate uptake in unilateral hydroxyapatite-coated total hip prostheses: First year of follow-up. J Nucl Med. 1994; 11: 1788–1791.

17.

Utz

Lull

Galvin

: Asymptomatic total hip prosthesis: Natural history determined using Tc-99m-MDP bone scans. Radiology 1986; 161: 509–512.

18.

Rosenthall

Brooks

: Differences between porouscoated S-ROM and AML hip prostheses determined by radioisotope uptake measurements and radiographic assesment. In: Galante

Rosenberg

Callaghan

, eds. Total hip revision surgery. New York, NY, USA; 1995: 203–212.

19.

Oswald

Van Nostrand

Savory

: Three-phase bone scan and indium white blood cell scintigraphy following porous coated hip arthroplasty: A prospective study of the prosthetic tip. J Nucl Med. 1989; 30: 1321–1331.

20.

Nakamura

: Measurement of periprosthetic bone mineral density after cementless hip arthroplasty by dual energy X-ray absorptiometry: Longitudinal and cross-sectional evaluation. J Orthop Sci. 1996; 1: 113–122.

21.

Nishii

Sugano

Masuhara

: Longitudinal evaluation of time related bone remodeling after cementless total hip arthroplasty. Clin Orthop 1997; 339: 121–131.

22.

Wixson

Stulberg

Van Flandern

: Maintenance of proximal bone mass with an uncemented femoral stem analysis with dual-energy X-ray absorptiometry. J Arthroplasty 1997; 4: 365–372.

23.

Rosenthall

: Hip and knee prostheses: Evaluation of the natural history of periprosthetic bone changes. Semin Nucl Med. 1997; 4: 346–354.

Periprosthetic Bone Turnover after Primary Total Hip Arthroplasty Measured by Single-Photon Emission Computed Tomography

Abstract

Background and Aims:

Material and Methods:

Results:

Conclusions:

Keywords

INTRODUCTION

MATERIALS AND METHODS

PATIENTS

SPECT

DXA

STATISTICAL ANALYSIS

RESULTS

DISCUSSION

Footnotes

ACKNOWLEDGEMENTS

References