Weight changes and the risk of knee osteoarthritis requiring arthroplasty.

OBJECTIVE: To examine the effect of weight changes between 20 and 50 years of age on the risk of severe knee osteoarthritis (OA) requiring arthroplasty. SUBJECTS AND METHODS: Cases were 55-75 year old men and women (n = 220) having had knee arthroplasty for primary osteoarthritis at the Kuopio University Hospital in 1992-93. Controls (n = 415) were randomly selected from the population of Kuopio Province. Weight at the age of 20, 30, 40, and 50 years was collected retrospectively with a postal questionnaire. RESULTS: After adjustment for age, sex, history of physical workload, recreational physical activity, and previous knee injury, weight gain resulting to a shift from normal body mass index (BMI < or =25 kg/m(2)) to overweight (BMI >25 kg/m(2)) was associated with a higher relative risk of knee OA requiring arthroplasty than persistent overweight from 20-50 years of age, compared with those with normal relative weight during the corresponding age period. The odds ratios (OR) were 3.07 (95% confidence interval 1.87 to 5.05) for those with normal weight at the age of 20 years and overweight at two or three of the ages 30, 40 or 50 years, 3.15 (1.85 to 5.36) for those with overweight from the age of 30 years, and 2.37 (1.21 to 4.62) for those with overweight from the age of 20 years, respectively. CONCLUSION: In adult life, a shift from normal to overweight may carry a higher risk for knee OA requiring arthroplasty than does constant overweight.

Effect of alendronate on periprosthetic bone loss after total knee arthroplasty: a one-year, randomized, controlled trial of 19 patients.

Undesired bone loss around implants is considered to occur mainly because of a stress-shielding phenomenon. Bone surrounding the total knee arthroplasty (TKA) adjusts its mineral density and structure to meet new mechanical demands. Immobilization, in combination with local operative trauma to the bone and soft tissues, has an additional impact on bone loss. The clinical survival of TKA is associated with the quality and quantity of the surrounding bone environment. Poor bone quality and quantity may predispose to aseptic implant loosening and periprosthetic fractures. We investigated the efficacy of oral bisphosphonate (alendronate, Fosamax) with calcium (Calcichew) for the inhibition of early bone mineral density (BMD) loss after TKA in a prospective, randomized, one-year follow-up study. Periprosthetic BMD changes were measured with fan-beam dual-energy X-ray absorptiometry (DXA) in 19 patients with knee osteoarthrosis. Patients (n = 8) treated with 10 mg alendronate and 500 mg calcium daily maintained distal femoral BMD values close to the baseline values (P > 0.04), while patients receiving only 500 mg of calcium daily (n = 11) showed significant bone loss during the one-year follow-up (P < 0.015). The treatment groups differed significantly in metaphyseal anterior, posterior, diaphyseal, and metaphyseal total regions of interest (ROIs) (repeated measures ANOVA analyses, P = 0.019, P = 0.010, P = 0.022, and P = 0.024, respectively). Our results indicate that oral alendronate reduces early postoperative periprosthetic bone loss significantly. This therapeutic strategy may improve the results and longevity of primary total knee arthroplasties.

Percutaneous bone grafting in the treatment of the delayed union and non-union of tibial fractures.

The classic method of open bone grafting in the treatment of un-united tibial fractures has been associated with some complications. A novel, minimally invasive, percutaneous technique of bone grafting is described. Forty-one consecutive patients with delayed union or non-union of a tibial fracture was treated with percutaneous bone grafting from 1993 to 1999. The mean age of the patients was 41 (15-86) years. Twenty-seven patients had grade I-III open fractures. The fractures had initially been treated in a cast (n=26), external fixator (n=14) or intramedullary nail (n=1). Two patients had an earlier unsuccessful Phemister-Charnley-type bone-grafting procedure for delayed union. The mean interval from injury to percutaneous bone grafting was 21 (13-66) weeks. Thirty-seven of the 41 un-united fractures healed in 13 (10-48) weeks after the percutaneous bone grafting. The mean hospital stay was 1 day. No infections, bleeding or neural complications existed. Percutaneous bone grafting appeared to be as effective as open techniques, and possessed considerable advantages. It is safe, time saving and economical, it involves minimal trauma at the fracture site and it avoids major donor site problems.

Bone mineral density after the removal of intramedullary nails: a cross-sectional and longitudinal study.

We measured bone mineral density (BMD) using dual X-ray absorptiometry (DXA) at several sites in both fractured and nonfractured limbs in eight patients with femoral shaft fracture and six with tibial shaft fracture at the time of the intramedullary (IM) nail removal. Seven patients were followed up for an average of 13 months. The BMD at the proximal part of the femur and tibia was from 3% to 11% lower in the fractured side as compared to the nonfractured side. The greatest bone loss (13%-21%) was found in the operated distal tibia of the patients with tibial shaft fractures. At the fracture site of the femur, BMD was 10.5% ( P < 0.05) higher, possibly owing to fracture callus formation, whereas tibial shaft BMD was not increased. However, a calculated apparent volumetric BMDvol at the fracture site was 15%-16% decreased. Although BMDs of the fractured side almost reached the baseline level of the nonfractured side (96.9%-102.1%) by the final follow-up (>12 months), the absolute deficit was still 3%-9%. Surprisingly, significant BMD increases (5%-6%) were also detected in all proximal femoral measurement sites of the contralateral limb, which indirectly suggests that the uninjured limb may also suffer from bone loss after lower-extremity trauma. We conclude that clinically important bone loss exists in the proximal femur and proximal and distal tibia of the fractured limb at the time of IM nail removal. Although areal BMD was higher at the femoral fracture site, the lower apparent volumetric BMDvol suggests decreased mineralization and reduced strength of the fracture site. Although the present results do not suggest special recommendations for restricted weight bearing after the removal of IM nails, the relationship between decreased bone density and increased risk of fractures should be borne in mind.

Alendronate reduces periprosthetic bone loss after uncemented primary total hip arthroplasty: a prospective randomized study.

Periprosthetic bone loss, especially in the proximal part of the femur, is common after cemented and uncemented total hip arthroplasty (THA). Bone loss can be progressive and, in the extreme, may threaten survival of the prosthesis. To study whether alendronate therapy can reduce bone loss adjacent to prostheses, 13 uncemented primary THA patients were randomized to the study. They received 10 mg alendronate + 500 mg calcium (n = 8) or 500 mg calcium only (n = 5) daily for 6 months follow-up after THA. Periprosthetic bone mineral density (BMD) was measured with dual energy X-ray absorptiometry (DXA). Decreases in periprosthetic BMD in the alendronate-treated group were lower compared with the changes in the calcium-only group in the same regions of interest at the same follow-up time. In the proximal femur, the mean BMD decrease was 17.1% in the calcium-only group, whereas in the alendronate-treated group the decrease was only 0.9% (p = 0.019). The mean periprosthetic BMD change was also significantly different in the total periprosthetic area between the study groups at the end of the follow-up (calcium-only group -9.9% vs. alendronate-treated group -2.6%; p = 0.019). Alendronate therapy led to a significant reduction in periprosthetic bone loss after primary uncemented THA compared with the changes found in patients without therapy. This kind of bone response may improve the support of the prosthesis and may result in better survival of the prosthesis. However, in this study the follow-up time was too short and the study population was too small to make any long-term conclusions as to the prognosis for THA patients treated with alendronate.

Monitoring of periprosthetic BMD after uncemented total hip arthroplasty with dual-energy X-ray absorptiometry--a 3-year follow-up study.

Insertion of a metallic implant into the femur changes bone loading conditions and results in remodeling of femoral bone. To quantify changes in bone mass after uncemented total hip arthroplasty (THA), we monitored femoral bone with dual-energy X-ray absorptiometry (DXA). The periprosthetic bone mineral density (BMD) was measured with Lunar DPX densitometry in seven Gruen zones and the total periprosthetic area at scheduled time intervals in 22 patients during a 3-year follow-up. BMD decreased significantly almost in all Gruen zones during the first 3 months, ranging from 3.4% to 14.4% (p < 0.05 top < 0.001). At the end of the first year, the most remarkable decrease in BMD was found in the calcar (zone 7; -22.9%). During the second postoperative year, a slight restoration of periprosthetic bone mass was recorded. During the third year, no significant changes in BMD were found. The preoperative BMD was the only factor that was significantly related to the periprosthetic bone loss. Clearly, the early periprosthetic bone loss noticed during the 3 months after THA is caused by mainly limited weight bearing to the operated hip and stress shielding. We suggest that the restoration of bone mass is a sign of successful osteointegration between bone and metallic implant. DXA is a suitable tool to follow the bone response to prosthetization and will increase our knowledge on the behavior of bone after THA.

Physical exercise and risk of severe knee osteoarthritis requiring arthroplasty.

OBJECTIVES: To examine the association between physical exercise and the risk of severe knee osteoarthritis requiring arthroplasty. SUBJECTS AND METHODS: A case-control study was carried out in which the cases were men (n=55) and women aged 55-75 yr (n=226) receiving knee arthroplasty for primary osteoarthritis at the Kuopio University Hospital. Controls (n=524) were selected randomly from the population of Kuopio province. Lifetime physical exercise was assessed retrospectively. Cumulative exercise hours were calculated and divided into two classes by mean (low/high). RESULTS: The risk of knee osteoarthritis requiring arthroplasty decreased with increasing cumulative hours of recreational physical exercise. After adjustment for age, body mass index, physical work stress, knee injury and smoking, the odds ratios (with 95% confidence intervals) of knee arthroplasty were 0.91 (0.31-2.63) in men with a low number of cumulative exercise hours and 0.35 (0.12-0.95) in those with a high number of cumulative exercise hours, with a history of no regular physical exercise as the reference. For the women, the corresponding odds ratios were 0.56 (0.3-0.93) and 0.56 (0.32-0.98). CONCLUSION: Moderate recreational physical exercise is associated with a decrease in the risk of knee osteoarthritis.

Bone loss around failed femoral implant measured by dual-energy X-ray absorptiometry.

Periprosthetic bone mineral density (BMD) and its changes after primary total hip arthroplasty (THA) have been studied extensively, but quantitative data on BMD around loosened prostheses are still lacking. In this study, using dual-energy X-ray absorptiometry (DXA), we determined periprosthetic BMD in 19 patients with failed primary THA. There was a decrease in BMD (8. 8%-25.5%) in every Gruen zone as compared with the patient's non-operated (control) side. Although the bone loss was most significant in the proximal femur, as in primary THA, the pattern of bone loss around the failed THA differred from the typical remodeling seen after successful THA. We suggest that quantitation of bone mass around the failed femoral stem is possible. Remarkable generalized bone loss around the stem is associated with a loosened prosthesis.

Measurement of bone density around total knee arthroplasty using fan-beam dual energy X-ray absorptiometry.

The clinical survival of joint arthroplasties is clearly associated with the quality of surrounding bone environment. Bone mineral density (BMD) is an important measure of bone strength and quality. Periprosthetic BMD can be measured by using dual-energy X-ray absorptiometry (DXA) with special software algorithms. We studied short-term reproducibility of the periprosthetic BMD measurements after total knee arthroplasty (TKA) in 30 patients with primary osteoarthrosis. The operated knees and the contralateral control knees were measured twice and the results were expressed as a coefficient of variation (CV%). The average precision error was 3.1% in femoral regions of interest (ROI) and 2.9% in tibial ROIs after TKA. In the prosthesis-free control knees, CV% were similar; 3.2% and 2.5%, respectively. The best precision was found in the femoral diaphyses above the implant (1.3%), whereas the least reproducible BMD was determined in the patellar region of the TKA knees (6.9%). Our results confirm that DXA measures precisely small bone mineral changes around TKA and makes it possible to follow bone remodeling DXA and may provide a feasible method for monitoring TKA in the future.

Computed tomography findings 4 years after surgical management of lumbar spinal stenosis. No correlation with clinical outcome.

STUDY DESIGN: A prospective, cross-sectional study of the correlation between postoperative computed tomography findings and patients' clinical outcomes approximately 4 years after laminectomy for lumbar spinal stenosis. OBJECTIVES: To evaluate clinical and radiologic characteristics and their relation to each other. SUMMARY OF BACKGROUND DATA: The goal of surgical management for lumbar spinal stenosis is to decompress the stenotic area determined in radiologic examinations to relieve pressure on the neurovascular structures. However, the success of this decompression very rarely has been confirmed by postoperative radiologic imaging or compared with clinical outcome. METHODS: Postoperative computed tomography was performed on 191 patients. The findings were classified as "no stenosis," "central stenosis," "lateral stenosis," or "central-lateral stenosis." Postoperative instability of the lumbar spine was investigated by functional radiography. Clinical status was assessed by clinical examination. Subjective disability was assessing using the Oswestry questionnaire, and severity of pain using the visual analog scale. Walking capacity was evaluated by the tread-mill test. RESULTS: Radiologic studies revealed postoperative stenosis in 123 patients (64%). Small differences between the computed tomography groups were shown for the Oswestry score, but not for walking distance. Clinical signs, severity of pain, and radiologic instability were very similar for all computed tomography groups. CONCLUSIONS: Postoperative radiologic stenosis was very common in patients operated on for lumbar spinal stenosis, but this did not correlate with clinical outcome. The clinician must be cautious when reconciling clinical symptoms and signs with postoperative computed tomography findings in patients operated on for lumbar spinal stenosis.

Long-term clinical and magnetic resonance imaging follow-up assessment of patients with lumbar spinal stenosis after laminectomy.

STUDY DESIGN: A cross-sectional retrospective study to observe the correlation between postoperation findings shown on magnetic resonance imaging and clinical observations of 56 patients 10 years after laminectomy for lumbar spinal stenosis. OBJECTIVE: To evaluate the relation between postoperation findings on magnetic resonance imaging and surgical outcome in patients surgically treated for lumbar spinal stenosis. SUMMARY OF BACKGROUND DATA: Surgical management of lumbar spinal stenosis is based on the compression seen in radiologic imaging of neurovascular structures in the vertebral canal, but the success of surgical decompression and its correlation with clinical observations very seldom have been monitored by postoperation radiologic imaging. METHODS: In this study, 56 patients surgically treated for lumbar spinal stenosis were re-examined clinically by use of the Oswestry disability questionnaire. Their walking capacity was evaluated by the treadmill test. Severity of pain before and after the treadmill test was investigated using a visual analog scale. Patients' perception of improvement measured as the change in their condition during the preceding 5 years was elicited by a questionnaire. On the basis of the stenotic findings on magnetic resonance imaging, the patients were classified into no stenosis (NoSten, n = 15) and stenosis (Sten, n = 41) groups, and a summative degenerative scale also was constructed with the findings categorized as follows: disc degeneration, disc herniation, facet joint arthrosis, and degenerative spondylolisthesis. RESULTS: Whereas the patients' perception of improvement correlated very strongly with the Oswestry score and walking capacity, there was no statistical difference between the NoSten and Sten groups in the Oswestry score, walking capacity, perception of improvement, or severity of pain. The effect of the summative degenerative scale on the patients' walking capacity was 13 times greater than the effect of the minimum area of the dural sac. CONCLUSIONS: Patients' perception of improvement had a much stronger correlation with long-term surgical outcome than structural findings seen on postoperation magnetic resonance imaging. Moreover, degenerative findings had a greater effect on patients' walking capacity than stenotic findings.

The degree of decompressive relief and its relation to clinical outcome in patients undergoing surgery for lumbar spinal stenosis.

STUDY DESIGN: A cross-sectional, clinical study to evaluate surgical decompression of the stenotic area monitored by computed tomographic scan and its relation to clinical variables in patients operated on for lumbar spinal stenosis. OBJECTIVE: To study in patients with lumbar spinal stenosis the influence of the degree of compressive relief on the patients' clinical outcome. SUMMARY OF BACKGROUND DATA: The goal of surgical treatment in lumbar spinal stenosis is to decompress the stenotic area. Although the decompression should be adequate, there are no clear guidelines to determine the extent of necessary decompression. In fact, there is clinical evidence that there is a discrepancy between the surgical outcome in the patient with lumbar spinal stenosis and postoperative radiologic findings. METHODS: In 92 patients with lumbar spinal stenosis who had had no prior back surgery, preoperative and postoperative computed tomographic scans were obtained to determine the degree of decompression. The postoperative scan findings were classified according to the degree of decompression into a no-stenosis group (n = 35), an adjacent-stenosis group (n = 27), and a residual-stenosis group (n = 30). The postoperative instability of the lumbar spine was investigated by functional radiography. The subjective disability of the patients was assessed using the Oswestry score and the severity of pain using the visual analog scale. Walking capacity was evaluated by a treadmill test. The patients' estimations of the results of surgery were classified into groups of satisfied patients and dissatisfied patients. RESULTS: The mean Oswestry score in all 92 patients was 27.1, and mean walking capacity was 630 m. In the satisfied patients, the Oswestry score was 18.8 and in the dissatisfied patients, 34.9 (P < 0.0000). Walking capacity was 690 m and 594 m, respectively. There were 30 patients with postoperative spinal instability, but it had no influence on surgical outcome. There were no differences in the Oswestry score, walking capacity, and patients' satisfaction among the postoperative CT groups. In the linear regression analysis, the satisfied patient corresponded significantly with the Oswestry score. CONCLUSIONS: The satisfaction of the patients with the results of surgery was more important in surgical outcome than the degree of decompression detected on computed tomographic scan.

Bone density at the proximal femur after total hip arthroplasty.

Recent developments in dual xray absorptiometry have made it possible to quantify bone mineral density changes adjacent to total hip arthroplasty. Even small changes in local bone mass that are not visible with conventional radiographs can be detected using dual xray absorptiometry. Commonly there is a loss of 10% to 45% of the periprosthetic bone mass during the first years after total hip arthroplasty. Recent studies have suggested that this bone loss is not necessarily progressive and some degree of restoration of bone density around implants may occur. Current data suggest that there is active bone remodeling in the proximal femur in response to prosthetic implantation. Such response differs between different stem designs and type of fixation.

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.

Single photon emission computed tomography (SPECT) at 6 and 12 months and dual-energy X-ray absorptiometry (DXA) at 0, 6, and 12 months were performed prospectively in 15 patients who had undergone uncemented total hip arthroplasty (THA) without any complications. Periprosthetic bone mineral density (BMD) decreased significantly in all regions of interests (ROIs) during 1 year of follow-up. The greatest annual decrease was found in the lesser trochanter region (22.1%). From 6-12 months, SPECT activity in the operated side decreased significantly (10-24%) in all ROIs, with the exception of the medial cortex ROI. In contrast, increases (8-36%) were found in the contralateral side. At 12 months, the operated versus control difference was still 10% in the lesser trochanter ROI, but as much as about 70% in the greater trochanter and tip ROIs. The decrease in BMD was significantly related to an increase in SPECT activity in the lesser trochanter region (r = -0.589, p < 0.05). In conclusion, increased periprosthetic SPECT activity seems to be associated with increased bone loss. We suggest that increased SPECT activity and subsequent bone loss reflect altered stress distribution and bone remodeling in the femur after prosthesis implantation.

Evaluation of periprosthetic bone using dual-energy x-ray absorptiometry: precision of the method and effect of operation on bone mineral density.

To assess the perioperative bone loss of femur during total hip arthroplasty (THA), periprosthetic bone mineral density (BMD) of the seven regions of interests (Gruen zones) was determined with dual-energy x-ray absorptiometry (DXA) preoperatively in both proximal femurs and postoperatively in the involved side in 53 patients with degenerative hip osteoarthrosis. The mean (standard deviation, SD) precision error (coefficient of variation percent, CV%) in various regions of interest (ROIs) based on two consecutive measurements (n = 16) were 2.3 (0.8)%, 2.5 (1.5)%, and 2.8 (1.6)% for uncemented stems, cemented stems, and control sides, respectively. Furthermore, the mean variability caused by the rotation of femur was 3.5 (1.4)%. The most significant perioperative bone loss (13.5-19.2%) was found in the calcar area (zone 7) after noncemented THA. Zone 4, representing the bone below the prosthesis, also showed BMD decreases. These decreases suggest perioperative bone loss owing to rasping and reaming the calcar and bone canal. However, after cemented THA, highly significant BMD increases were found in all the lateral zones. The calcar area was the only site where significant perioperative bone loss was detected (12.8%). In conclusion, DXA is a precise method for quantifying bone mass and density changes in the follow-up of THA. However, when interpreting the results, the preoperative BMD, differences between the femurs and the effect of operation on bone mass should be taken into account. We suggest that the best reference for BMD follow-up is the periprosthetic BMD of the involved side measured soon after the THA.

Intra-articular hyaluronan injections in the treatment of osteoarthritis of the knee: a randomised, double blind, placebo controlled multicentre trial. Hyaluronan Multicentre Trial Group.

OBJECTIVE: To assess the effects of intra-articular injections of hyaluronan on symptoms of knee osteoarthritis (OA). METHODS: Two hundred and forty patients with symptomatic, radiological knee OA were randomly assigned to treatment with weekly injections for five weeks with either 25 mg of high molecular weight hyaluronan or vehicle. Results were evaluated at weeks 1, 2, 3, 4, 5, 13, and 20 by visual analogue scales (pain, function, motion, activity), algofunctional index, and global evaluation by patient and investigator. Analysis was by "intention to treat', "per protocol', and area under the curve principles on unstratified patient groups and for patients stratified into four groups of equal size by age and baseline algofunctional index. RESULTS: No serious side effects were reported. At 20 weeks both treatment groups were improved compared with baseline, with no difference between unstratified groups treated with placebo or hyaluronan. Comparison of treatment groups stratified by age and baseline algofunctional index revealed a significant difference in favour of hyaluronan over placebo (pain, activity, algofunctional index, global evaluations by patient and investigator) for patients older than 60 years and with a baseline algofunctional index greater than 10. There was no clinically relevant difference between the two treatments for the other three stratified subgroups of younger age or fewer symptoms. Similar results were obtained by area under the curve, intention to treat, and per protocol analysis. CONCLUSIONS: Patients older than 60 years with knee osteoarthritis and with significant symptoms corresponding to an index of severity of knee disease of 10 or more, comprise the group most likely to benefit from treatment with intra-articular hyaluronan injections.

Prevention of fatal pulmonary embolism with warfarin after total hip replacement.

We studied retrospectively the efficacy of low-dose warfarin for the prevention of fatal pulmonary embolism in 1140 patients (1280 hips) undergoing total hip replacement between 1972 and 1989. The first dose, 10-20 mg, was given the night before operation and the regime was continued for 2 weeks after the procedure. Anticoagulation was aimed at achieving a therapeutic level in 4 to 5 days. All the patients were followed for 3 months. Seven died during this period and autopsy showed that 2 (0.16%) died from pulmonary embolism, one at 3 days and the other 10 days after operation. Pulmonary embolism causing symptoms, but which was not fatal, occurred in 32 patients (2.5%). Symptomatic deep vein thrombosis was present in 45 patients (3.5%). There were 14 (1.1%) massive postoperative haematoma, and 7 needed operative treatment. Low-dose warfarin can be recommended as a safe and efficient method of achieving an acceptably low incidence of postoperative thrombo-embolic complications after total hip replacement.

Density of lumbar muscles 4 years after decompressive spinal surgery.

Results of decompressive surgery for lumbar spinal stenosis vary. We evaluated the density of lumbar muscles by computed tomography (CT) at the L2-L4 levels in patients 4 years after they had undergone surgery for lumbar spinal stenosis. Twenty of these patients had an excellent outcome clinically, and 16 patients had very poor outcome. The residual stenosis and density of lumbar muscles in Hounsfield units were measured on CT images. The clinical evaluation of outcome also included the Oswestry questionnaire and a walking test. The density of lumbar flexors was higher in the group with excellent results than in the group with poor results. The density of lumbar extensors showed a marked decrease in the operated area. These results suggest that the decrease of muscular density can be partially explained by disuse or inactivity. The decrease in the operated area probably reflects muscular atrophy caused by muscle denervation.

Prophylaxis for the prevention of venous thromboembolism after total knee arthroplasty. A comparison between unfractionated and low-molecular-weight heparin.

We compared the efficacy and safety of low-molecular-weight heparin with that of low-dose unfractionated heparin in the prevention of venous thromboembolism after total knee arthroplasty in a prospective, randomized, multicenter trial. One hundred and eighty-five patients were randomly assigned to two groups: ninety-two received low-molecular-weight heparin (forty milligrams of enoxaparin the evening before the operation and once a day subsequently) and ninety-three received unfractionated heparin (5000 international units the evening before the operation and three times a day thereafter). The prophylaxis was continued until bilateral ascending venography was performed six to nine days after the operation or, if venography was not done, until the eighth postoperative day. Venography revealed a prevalence of deep-vein thrombosis of 27 per cent (twenty-five of ninety-three patients) in the group that received unfractionated heparin and 23 per cent (twenty-one of ninety-two patients) in the group that received low-molecular-weight heparin. The difference was not significant (p = 0.6). Five patients (5 per cent) who received unfractionated heparin and 3 patients (3 per cent) who received low-molecular-weight heparin had a deep-vein thrombosis in the proximal veins. Two patients who received unfractionated heparin and one who received low-molecular-weight heparin had clinical symptoms suggestive of a pulmonary embolism. None of these three patients had a positive ventilation-perfusion scan. There were no deaths, major bleeding episodes, or wound hematomas necessitating operative intervention or discontinuation of the anticoagulation in the series.(ABSTRACT TRUNCATED AT 250 WORDS)