Prevention of heterotopic ossification (HO) after total hip replacement: randomized high versus low dose radiotherapy

Neutrophil and NETosis Modulation in Traumatic Heterotopic Ossification

OBJECTIVE

To characterize the role of neutrophil extracellular traps (NETs) in heterotopic ossification (HO) formation and progression and to use mechanical and pharmacological methods to decrease NETosis and mitigate HO formation.

BACKGROUND

Traumatic HO is the aberrant osteochondral differentiation of mesenchymal progenitor cells after traumatic injury, burns, or surgery. While the innate immune response has been shown to be necessary for HO formation, the specific immune cell phenotype and function remain unknown. Neutrophils, one of the earliest immune cells to respond after HO-inducing injuries, can extrude DNA, forming highly inflammatory NETs. We hypothesized that neutrophils and NETs would be diagnostic biomarkers and therapeutic targets for the detection and mitigation of HO.

METHODS

C57BL6J mice underwent burn/tenotomy (a well-established mouse model of HO) or a non-HO-forming sham injury. These mice were either (1) ambulated ad libitum, (2) ambulated ad libitum with daily intraperitoneal hydroxychloroquine, ODN-2088 (both known to affect NETosis pathways), or control injections, or (3) had the injured hind limb immobilized. Single-cell analysis was performed to analyze neutrophils, NETosis, and downstream signaling after the HO-forming injury. Immunofluorescence microscopy was used to visualize NETosis at the HO site and neutrophils were identified using flow cytometry. Serum and cell lysates from HO sites were analyzed using enzyme-linked immunosorbent assay for myeloperoxidase-DNA and ELA2-DNA complexes to identify NETosis. Micro-computerized tomography was performed on all groups to analyze the HO volume.

RESULTS

Molecular and transcriptional analyses revealed the presence of NETs within the HO injury site, which peaked in the early phases after injury. These NETs were highly restricted to the HO site, with gene signatures derived from both in vitro NET induction and clinical neutrophil characterizations showing a high degree of NET "priming" at the site of injury, but not in neutrophils in the blood or bone marrow. Cell-cell communication analyses revealed that this localized NET formation coincided with high levels of toll-like receptor signaling specific to neutrophils at the injury site. Reducing the overall neutrophil abundance within the injury site, either pharmacologically through treatment with hydroxychloroquine, the toll-like receptor 9 inhibitor OPN-2088, or mechanical treatment with limb offloading, results in the mitigation of HO formation.

CONCLUSIONS

These data provide a further understanding of the ability of neutrophils to form NETs at the injury site, clarify the role of neutrophils in HO, and identify potential diagnostic and therapeutic targets for HO mitigation.

Efficacy of ibuprofen and indomethacin as prophylaxis of heterotopic ossification: a comparative study

The prophylactic action of non-steroidal anti-inflammatory drugs (NSAIDs) in heterotopic ossification (HO) was first described following analgesic therapy with indomethacin. Following that evidence, several compounds have been successfully used for prophylaxes of HO. Ibuprofen has been also proposed for the prevention of HO following THA. The present study compared the administration of ibuprofen for three weeks versus indomethacin as prophylaxis for HO following primary THA. In all THA procedures, pre- and post-operative protocols were conducted in a highly standardized fashion. The type of HO prophylaxis (indomethacin 100 mg/daily or ibuprofen 100 mg/daily) was chosen according to a chronological criterion: from 2017 to 2019 indomethacin was used, whereas from 2019 to 2022 ibuprofen was administered. In case of allergy or intolerance to NSAIDs, no prophylaxis was performed, and patients were included as a control group. All patients who underwent an anteroposterior radiography of the pelvis at a minimum of 12 months following THA were considered for inclusion. On admission, the age and sex of the patients were recorded. Moreover, the causes of osteoarthritis and the date of surgery were recorded. The grade of HO was assigned by a blinded assessor who was not involved in the clinical management of the patients. The modified Brooker Staging System was used to rate the efficacy of the interventions. Data from 1248 patients were collected. 62% (767 of 1248 patients) were women. The mean age was 67.0 ± 2.9 years. The mean follow-up was 21.1 ± 10.8 months. In the ibuprofen group, 73% of patients evidenced Brooker 0, 17% Brooker I, and 10% Brooker II. In the indomethacin group, 77% of patients evidenced Brooker 0, 16% Brooker I, 6% Brooker II. No patient in the ibuprofen and indomethacin group developed Brooker III or IV. In the control group, 64% of patients evidenced Brooker 0, 21% Brooker I, 3% Brooker II, and 12% Brooker III. No patient in the control group developed Brooker IV HO. Concluding, three weeks of administration of ibuprofen demonstrated similar efficacy to indomethacin in preventing HO following primary THA. The prophylaxis with ibuprofen or indomethacin was more effective in preventing HO compared to a control group who did not receive any pharmacological prophylaxis.

Efficacy of NSAIDs versus radiotherapy for heterotopic ossification prophylaxis following total hip arthroplasty in high-risk patients: a systematic review and meta-analysis

BACKGROUND

The aims of this systematic review were: (1) to investigate the prophylactic effect of radiotherapy (RT) and NSAIDs in high-risk patients following total hip arthroplasty (THA); and (2) to compare the efficacy of non-selective and COX-II selective NSAIDs in preventing post-THA HO, utilising a meta-analysis of randomised control studies.

METHODS

The PubMed, Embase, and Cochrane Databases were searched for articles regarding HO following THA in March 2019. Studies were included if they contained data regarding HO incidence after THA or contained data regarding HO prophylaxis comparison of NSAIDs and/or RT in terms of dosage or duration.

RESULTS

24 studies reported on populations that were not at high-risk for HO. These studies reported between 47.3% and 90.4% of their patient populations had no HO formation; between 2.8% and 52.7% had mild formation; and between 0.0% and 10.4% had severe formation. A total of 13 studies reported on populations at high-risk for HO. Studies analysing RT in high-risk patients reported between 28.6% and 97.4% of patients developed no HO formation; between 1.9% and 66.7% developed mild HO formation; and between 0.0% and 11.9% developed severe HO formation. Studies analysing NSAID treatment among high-risk populations reported between 76.6% and 88.9% had no HO formation; between 11.1% and 23.4% had mild HO formation, and between 0.0% and 1.8% had severe HO formation. 9 studies were identified as randomised control trials and subsequently used for meta-analysis. The relative risk for COX-II in developing any HO after THA was not significantly different compared to non-selective NSAIDs (RR 1.00; CI, 0.801-1.256; p = 0.489).

CONCLUSIONS

NSAIDs prophylaxis for HO may have better efficacy than RT in high-risk patients following THA. Non-selective and COX-II selective NSAIDs have comparable efficacy in preventing HO. Factors such as medical comorbidities and side-effect profile should dictate the prophylaxis recommendation.

Selective versus non-selective NSAIDs as prophylaxis for heterotopic ossification following hip arthroplasty: a meta-analysis

Background

Some patients have demonstrated evidence of heterotopic ossification (HO) following total hip arthroplasty (THA). Selective and non-selective non-steroidal anti-inflammatory drugs (NSAIDs) are used as prophylaxis for HO following THA. This meta-analysis compared selective versus non-selective NSAIDs as prophylaxis for HO following THA.

Material and methods

The present study was conducted according to the PRISMA 2020 guidelines. All the clinical investigations comparing selective versus non-selective NSAIDs as prophylaxis for HO following THA were accessed in February 2022. An assessment of the methodological quality and statistical analyses were performed through the risk of bias summary tool of the Review Manager 5.3 software (Cochrane Collaboration, Copenhagen). The modified Brooker staging system was used to rate the efficacies of the interventions.

Results

Data from 8 studies and 1526 patients were collected. 60.8% were female. No difference was found in the sample size, mean age, and percentage of females between the two groups at baseline. No statistically significant difference was found between selective and non-selective NSAIDs in term of efficacy. 72% (1078 of 1502) of the patients were classified as Brooker 0, 21% (322 of 1502) as Brooker I, 5% (80 of 1502) as Brooker II, 1% (16 of 1502) as Brooker III, and 0.1% (2 of 1502) as Brooker IV.

Conclusion

Selective and non-selective NSAIDs were equally effective when used as prophylaxis for HO following THA.

Level of evidence

Level III, systematic review and meta-analysis.

Heterotopic Ossification: A Challenging Complication of Total Hip Arthroplasty: Risk Factors, Diagnosis, Prophylaxis, and Treatment

Background

This review is intended to summarize the risk factors, classification, diagnosis, and treatment of heterotopic ossification (HO) of previously published studies.

Results

Heterotopic ossification is a common complication of total hip arthroplasty. Its prevalence is not the same in all of the patient groups. Frequency of HO varies from 15 to 90%. Hip ankylosis, male gender, and previous history of HO are said to be risk factors with a significant level. Diagnosis is based on a single AP radiograph: the Brooker classification that divides HO into four grades is the most commonly used. The confirmation test that can be used is a bone scan. A great amount of bone metabolic turnover markers have been tested, but none of them seems to be relevant in case of prevention or diagnosis of HO. The most effective prophylactic treatment is radiotherapy or administration of nonsteroidal anti-inflammatory drugs. Over the years a lot of different RT protocols have been tested. Nowadays the most often used regimen is 7 Gy given postoperatively in a single dose. The most commonly prescribed drug in prophylaxis of HO is indomethacin. Also, the efficacy of ibuprofen and diclofenac was proven. Recently researchers focused on selective COX-2 inhibitors. They appear to be as effective as nonselective NSAIDs having less side effects. The one and only treatment of HO is a revision arthroplasty.

[Radiotherapy indications for non-malignant diseases in 2014]

This review updates the radiotherapy indications for non-malignant diseases, except those treated by radiosurgery. Since the last 2005 review, there have been no major changes in the indications: the prevention of heteropic bone formation and keloids remain classical indications, while the treatment of macular degeneration or the prevention of coronary restenosis are now past history. Nevertheless, the radiation treatment for benign diseases should have the same criteria as for malignant diseases: information of the patient on risks, benefits and treatment quality.

Blast injuries and heterotopic ossification

Heterotopic ossification (HO) is perhaps the single most significant obstacle to independence, functional mobility, and return to duty for combat-injured veterans of Operation Enduring Freedom and Operation Iraqi Freedom. Recent research into the cause(s) of HO has been driven by a markedly higher prevalence seen in these wounded warriors than encountered in previous wars or following civilian trauma. To that end, research in both civilian and military laboratories continues to shed light onto the complex mechanisms behind HO formation, including systemic and wound specific factors, cell lineage, and neurogenic inflammation. Of particular interest, non-invasive in vivo testing using Raman spectroscopy may become a feasible modality for early detection, and a wound-specific model designed to detect the early gene transcript signatures associated with HO is being tested. Through a combined effort, the goals of early detection, risk stratification, and development of novel systemic and local prophylaxis may soon be attainable.

Traumatic amputation — a contemporary approach

The management of patients with loss or near loss of a limb secondary to high-energy trauma is particularly challenging. Management consists of an acute phase of resuscitation and initial surgery, followed by a longer chronic phase, consisting of rehabilitation, fitting of a prosthesis and stump care. Acute assessment by the full trauma team along standard 〈C〉ABCDE guidelines should not conflict with early stemming of on-going stump or limb haemorrhage as required. Patients with traumatic limb loss are likely to be shocked and have traumatic coagulopathy; initial and on-going resuscitation should satisfy the need to replace blood with packed cells and plasma in a 1 : 1 ratio consistent with the concept of `Damage Control Resuscitation'. The surgical goal is to tailor surgery to the patients' physiological state, removing dead and unviable tissue, restoring perfusion to live tissue, stabilising fractured bone and addressing the loss of soft tissues. The imperative to preserve length should not outweigh the need to leave the patient with a stump that will heal in a timely fashion. Lifelong prosthetic preventive maintenance is paramount as residual limbs change in volume with muscle atrophy and changes inpatient weight. Replacement may also be indicated as improved designs appear from time to time. Early rehabilitation and prosthetic fitting also improves routine prosthetic use, which has been found to positively affect return to work.

Heterotopic ossification following traumatic and combat-related amputations. Prevalence, risk factors, and preliminary results of excision

BACKGROUND

Although infrequently reported in amputees previously, heterotopic ossification has proven to be a common and problematic clinical entity in our recent experience in the treatment of traumatic and combat-related amputations related to Operation Enduring Freedom and Operation Iraqi Freedom. The purpose of the present study was to report the prevalence of and risk factors for heterotopic ossification following trauma-related amputation as well as the preliminary results of operative excision.

METHODS

We identified 330 patients with a total of 373 traumatic and combat-related amputations who had been managed at our centers between September 11, 2001 and November 30, 2005. We reviewed the medical records and radiographs of 187 patients with 213 amputations who had adequate radiographic follow-up. Additional analysis was performed for twenty-four patients with twenty-five limbs that required excision of symptomatic lesions. The mechanism and zone of injury, amputation level, timing of excision, use of prophylaxis against recurrence, and other confounding variables were examined. Outcomes were assessed by determining clinical and radiographic recurrence rates, perioperative complications, preoperative and follow-up pain medication requirements, and the ability to be fit with a functional prosthesis.

RESULTS

Heterotopic ossification was present in 134 (63%) of 213 residual limbs, with twenty-five lesions requiring excision. A final amputation level within the zone of injury was a risk factor for both the development and the grade of heterotopic ossification (p < 0.05). A blast mechanism was predictive of occurrence (p < 0.05) but did not correlate with grade. All patients who had been managed with excision were tolerating the prosthetic limb at an average of twelve months of follow-up. Twenty-three limbs demonstrated no evidence of recurrence, and two limbs had development of clinically asymptomatic, radiographically minimal recurrences. Six patients experienced wound-related complications that required reoperation, and two patients required subsequent minor revision surgery. There was a significant decrease in the use of pain medication following surgery (p < 0.05).

CONCLUSIONS

Heterotopic ossification following trauma-related amputation is more common than the literature would suggest, particularly following amputations that are performed within the initial zone of injury and those that are due to blast injuries. Many patients are asymptomatic or can be successfully managed with modification of the prosthesis. For patients with refractory symptoms, surgical excision is associated with low recurrence rates and decreased medication requirements, with acceptable complication rates.

Heterotopic ossification in the residual limbs of traumatic and combat-related amputees

Reports on the occurrence and treatment of heterotopic ossification in amputees are rare. Heterotopic ossification in the residual limbs of amputees may cause pain and skin breakdown and complicate or prevent optimal prosthetic fitting and utilization. Basic science research has shed light on the cellular and molecular basis for this disease process, but many questions remain unanswered. The recent experience of the military amputee centers with traumatic and combat-related amputations has demonstrated a surprisingly high prevalence of heterotopic ossification in residual limbs. Primary prophylactic regimens, such as nonsteroidal anti-inflammatory drugs and local irradiation, which have proved to be effective in preventing and limiting heterotopic ossification in other patient populations, have not been studied in amputees and generally are not feasible in the setting of acute traumatic amputation. When nonsurgical measures such as activity and repeated prosthetic modifications fail to provide relief, surgical excision has provided good early clinical results, with low rates of recurrence and acceptable complication rates in military amputees.

La radiothérapie des affections bénignes : quelles indications huit ans plus tard ?

The authors present an update version of the indications for radiotherapy in the management of benign diseases. This is based on available randomized trials and recent international meetings. Validated indications remain the prevention of resected heterotopic bone ossifications, keloïds scars and pterygium and also treatment of arteriovenous malformations; the place of radiotherapy for malignant exophtalmia is more and more restricted. Randomized trials have demonstrated the efficacy of endobrachytherapy in the prevention of restenosis after angioplasty but the use of embedded stent has replaced this indication. Macular degeneration is no more an indication of radiotherapy. Quality requirements for radiotherapy are identical for benign or malignant indications.

Radiotherapy vs. nonsteroidal anti-inflammatory drugs for the prevention of heterotopic ossification after major hip procedures: a meta-analysis of randomized trials

PURPOSE

To evaluate the efficacy of radiotherapy (RT) vs. nonsteroidal anti-inflammatory drugs (NSAIDs) in the prevention of heterotopic ossification (HO) after major hip procedures.

METHODS AND MATERIALS

We conducted a meta-analysis of 7 randomized studies (n = 1143) comparing RT with NSAIDs. Data were combined across studies using fixed and random effects models. We conducted separate analyses for clinically significant HO (Brooker Grade 3 and 4) and for any HO (any Brooker grade).

RESULTS

Overall RT tended to be more effective than NSAIDs in preventing Brooker 3 or 4 HO (risk ratio, 0.42; 95% confidence interval [CI], 0.18-0.97) or any HO (risk ratio, 0.75; 95% CI, 0.37-1.71), but with significant between-study heterogeneity for the second analysis. The overall absolute risk difference for Brooker 3 or 4 HO was small (-1.18%; 95% CI, -2.45% to 0.09%). Subgroup analyses showed that early preoperative RT (16-20 hours before surgery) and acetylsalicylic acid were less effective. For postoperative RT, there was a significant dose-response relationship (p = 0.008): 6 Gy of RT was equally effective as NSAIDs, whereas increasing radiation doses were more effective.

CONCLUSIONS

Although absolute differences may be small, postoperative RT is on average more effective than NSAIDs in preventing HO after major hip procedures, and its efficacy is dose dependent.

Incidence of heterotopic bone formation after major hip surgery

BACKGROUND

Heterotopic bone formation is a well-established complication of major hip surgery, but traditional reviews of the published literature may have underestimated its frequency.

METHODS

A systematic overview of all the relevant studies was performed to determine reliably the incidence of any heterotopic bone formation and the incidence of each Brooker equivalent grade. Separate estimates were made for patients with total hip replacement and patients with acetabular fracture repair.

RESULTS

A computer-based search identified 218 studies with data on the incidence of heterotopic bone formation after either hip replacement or acetabular fracture repair. These studies included data from an estimated 59 121 operated hips among patients that received total hip replacement and an estimated 998 hips among patients that underwent acetabular fracture repair. In these studies, the incidence of any heterotopic bone formation was 43% after total hip replacement and 51% after acetabular fracture repair. The incidence of severe heterotopic bone formation was 9% and 19%, respectively.

CONCLUSIONS

These results suggest that heterotopic bone formation occurs more frequently after total hip replacement than is generally believed. It is possible that heterotopic bone formation is a more important cause of postoperative disability than has previously been recognized and that effective prophylactic regimens might improve outcome in substantial numbers of patients.

Radiation prophylaxis for heterotopic ossification about the hip joint--a multicenter study

PURPOSE

Prophylactic radiotherapy (RT) can prevent ectopic bone formation about the hip after total hip arthroplasty. The German Cooperative Group on Radiotherapy for Benign Diseases conducted a patterns of care study about this indication addressing the involved institutions, RT dose concepts, clinical handling, and treatment outcome of prophylactic RT about the hip joint.

METHODS AND MATERIALS

In 1999, a patterns of care study was conducted in all German institutions to analyze the accrual pattern, number of patients, and different indications for the use and performance of prophylactic RT about the hip. The applied RT concepts of prophylactic RT were evaluated with regard to the RT technique, timing of RT (pre- or postoperative), RT dose prescription (median, range of single and total doses), and treatment outcome. All institutions were asked about the radiologic and functional failure rates at least 1 year after the completion of RT using the established radiologic (Brooker) and functional (Harris) scores with objective and subjective evaluation components.

RESULTS

One hundred fourteen institutions reported their clinical experience with prophylactic RT for the prevention of heterotopic ossification about the hip joint: 70 community hospitals, 23 university hospitals, and 21 private RT practices. In 1999, 5677 patients (5989 hips) had received prophylactic RT. The median number per institution was 36 patients (range 8-240). The interdisciplinary referral included orthopedic surgery (89 institutions; 3763 patients), trauma surgery (82 institutions; 1611 patients), or other disciplines (8 institutions; 298 patients). Preoperative RT was applied in 53 institutions 0.5-24 h before surgery, and postoperative RT was applied in 54 institutions 1-120 h after surgery. Most patients received 1 x 7 Gy either pre- or postoperatively. The total dose range was 5-10 Gy (preoperative RT) or 5-16 Gy (postoperative RT); the median total RT dose of both RT concepts was 7 Gy. Cobalt-60 (n = 15), linear accelerators (n = 95), and a few lower energy units (n = 4) were used. Bony structures or prostheses were shielded with standard blocks in 31 and with individual blocks in 27 institutions. Long-term clinical evaluation was available in 30 institutions from 4377 hips. Of those, 475 (11%) developed radiologic failures according to Brooker's criteria. Functional hip evaluation was available in 5 institutions from 685 hips. Of those, 34 (5%) had functional failures according to the criteria of Harris. No difference in outcome was found between pre- and postoperative RT, but was with regard to the patient's referral and the timing of RT. The patients who were treated >8 h before surgery or >72 h after surgery experienced a higher radiologic failure rate; radiologic failures were an important precondition for functional failures (p <0.05).

CONCLUSION

This patterns of care study comprises the largest number of cases reported for prophylactic hip RT to date. The results reveal that both preoperative (within 24 h) and postoperative RT (within 72 h) are effective in preventing heterotopic ossification after hip surgery. Both RT concepts achieved a similar low radiologic and functional failure rate. Single-dose RT concepts, especially, can be recommended as an excellent treatment alternative for patients with contraindications to long-term steroid or nonsteroidal anti-inflammatory agents, and this approach has become standard in most German RT institutions.

[Role of radiotherapy in benign diseases]

Radiation therapy of benign diseases represent a wide panel of indications. Some indications are clearly identified as treatment of arteriovenous malformations (AVM), hyperthyroid ophtalmopathy, postoperative heterotopic bone formations or keloid scars. Some indications are under evaluation as complications induced by neo-vessels of age-related macular degeneration or coronary restenosis after angioplasty. Some indications remain controversial with poor evidence of efficiency as treatment of bursitis, tendinitis or Dupuytren's disease. Some indications are now obsolete such as warts, or contra-indicated as treatment of infant and children.

Prevention of heterotopic ossification about the hip: final results of two randomized trials in 410 patients using either preoperative or postoperative radiation therapy

PURPOSE

Experimental and clinical data support effectiveness of perioperative radiotherapy to prevent heterotopic ossification after hip surgery or trauma. Since 1987, two prospectively randomized trials were performed in patients with high-risk factors to develop heterotopic ossification: the first (HOP 1) to assess the prophylactic efficacy of postoperative low vs. medium dose radiotherapy, and the second (HOP 2) to assess the prophylactic efficacy of pre vs. postoperative radiotherapy.

METHODS AND MATERIAL

410 patients with high risk to develop heterotopic ossifications about the hip following hip surgery were recruited. Between June 1987 and June 1992, 249 patients were randomized in HOP 1 to postoperative "low dose" (5 x 2 Gy; total: 10 Gy) or "medium dose" (5 x 3.5 Gy; total: 17.5 Gy) radiotherapy. Between July 1992 and December 1995, 161 patients were randomized in HOP 2 to either 1 x 7 Gy preoperatively (< or = 4 h before surgery) or 5 x 3.5 Gy (total: 17.5 Gy) postoperatively (< or = 96 h after surgery). With exception of age and type of implant (cemented vs. uncemented prosthesis) all confounding patient variables (gender, prior surgery) and predisposing risk factors were similarly distributed between both trials and treatment arms. Portals encompassed the periacetabular and intertrochanteric soft tissues. Radiographs were obtained prior and immediately after surgery and at least 6 months after surgery to assess the extent of ectopic bone formation about the hip. Modified Brooker grading was used to score the extent of heterotopic ossification. Harris scoring was applied to evaluate the functional hip status. If the scores decreased from immediate post or preoperative status, respectively, to the last follow-up, radiological or functional failures were assumed.

RESULTS

Effective prophylaxis was achieved in 227 (91%) hips of HOP 1 and in 142 (88%) of HOP 2. In HOP 1, 15 (11%) radiological failures were observed in the low-dose group compared to 7 (6%) in the medium dose group (p > 0.05). In HOP 2, 4 (5%) radiological failures were observed in the postoperative and 11 (19%) in the preoperative group (p < 0.05). Subgroup analysis of the preoperative group revealed that the highest failure rate occurred in patients with prophylactic radiotherapy prior to removal of ipsilateral Brooker Grade III and IV ossification (39%) (p < 0.001), while all other patients in the preoperative group had a failure rate that was comparable to postoperative treatment groups. In multivariate logistic regression analysis the number of high-risk factors for development of heterotopic ossification (p = 0.03) and the time to RT initiation (p = 0.05) were independent prognostic factors in the HOP 1 study. For the HOP 2 study, the multivariate logistic regression analysis revealed the number of high-risk factors for development of heterotopic ossification (p = 0.003), the preoperative HO grade (p = 0.001) and the RT dose concept (p = 0.05) as independent prognostic factors. Other factors including type of implant (cemented vs. uncemented) did not affect the prophylactic efficacy of radiotherapy. There were no increased intra- and postoperative complications seen in the preoperative group, and no long-term complications were observed in both HOP studies. For functional failures (decrease of Harris score) no statistically prognostic factors were found. There were less functional failures in HOP 1 (18 = 7%) than in HOP 2 (23 = 14%, but this difference was not statistically significant. Only patients with high Brooker Grade III and IV at last FU achieved a lower Harris score than those with low Brooker Grade 0, I and II (p < 0.05).

CONCLUSION

With the exception of a small subgroup of patients with ipsilateral high Brooker Grade III and IV, pre- and postoperative radiotherapy are equally effective to prevent heterotopic ossification about the hip after hip surgery and total hip arthroplasty. Fractionated medium dose radiotherapy resulted in the low

Heterotopic bone formation affecting the hip joint is preventable in high risk patients by post-operative radiation

Between 1984 and 1993, 40 high risk patients (45 hips) received postoperative irradiation as prophylaxis against heterotopic ossification (HO). Radiotherapy was commenced within 5 days of the surgery in 43 of 45 hips. The development of HO was assessed by comparison of radiographic films prior to irradiation and at least 2 months after treatment (median interval 12 months). Progression of HO was observed in only two of 45 hips (4.3%) and of clinical significance in one (2.2%). Treatment was well tolerated with no acute complications or loosening of prosthetic components attributable to irradiation. During the study period, the treatment programme changed from 20 Gy in 10 fractions to 6-8 Gy in a single fraction, without loss of treatment efficacy. As well as improving resource utilization, single fraction techniques allow fewer patient transfers thereby reducing patient discomfort and risk of hip dislocation. This procedure is uncomplicated and should be considered more widely in the management of this disabling non-malignant condition.

Preoperative versus postoperative radiotherapy for prevention of heterotopic ossification (HO): first results of a randomized trial in high-risk patients

PURPOSE

In vivo data support the effectiveness of pre- and postoperative radiotherapy in suppressing the development of heterotopic ossification after hip surgery. In June 1992 a prospectively randomized trial was initiated to assess the comparative efficacy of pre- vs. postoperative prophylactic radiotherapy in patients with high risk to develop heterotopic ossification after hip surgery.

METHODS AND MATERIAL

Between June 1992 and September 1993 a total of 84 eligible patients with high risk profile for the development of heterotopic ossification were entered in the study. They were randomized to receive radiotherapy either preoperatively (< 4 h before surgery) or according to a "standard protocol" postoperatively (< 72 h after surgery). A single 7 Gy fraction was administered to the preoperative group, while the postoperative group received a previously tested scheme of five fractions of 3.5 Gy (total dose 17.5 Gy). The treatment portal encompassed the soft tissues between the periacetabular region of the pelvis and the intertrochanteric portion of the femur. Important patient variables (age, sex, prior surgery) and predisposing risk factors were equally distributed between both treatment arms. X rays of the irradiated hips were obtained prior and immediately after surgery as well as at 6 months after surgery. The modified Brooker grading was used to score the extent of heterotopic ossification. The Harris score was applied to judge the overall functional status of the hip. If the Brooker grade and Harris score decreased from the immediate postoperative or preoperative status respectively to the follow-up situation, the case was considered as a "treatment failure."

RESULTS

At a minimum 6 months follow-up after hip surgery 44 patients were available for evaluation. Effective prophylaxis was achieved in 41 (93%) hips. Two "radiological failures" were observed in the preoperative group and one in the postoperative group. Neither the pre- nor the postoperative interval affected the prophylactic efficacy. There were no increased intra- and postoperative complications seen in the preoperative group. The interval of partial strain (50% body weight) to the operated hip was longer in the preoperative group (19 days +/- 27) as compared to the postoperative group (8 days +/- 13), however the interval to full strain (100% body weight) was equal in both groups. The functional status (Harris Score change) of the operated hip decreased only in two (5%) patients ("functional failures"). The overall change was better in the postoperative group (42.7 +/- 17.1) as compared to the preoperative group (34.3 +/- 13.7) (p = 0.08, NS) as well as with regard to the criteria "limp" (p = 0.05) and "use of walking support" (p = 0.10, NS). In in all other aspects no differences were observed between both treatment arms. Therefore, the preliminary results for preoperative radiotherapy are similar to historical results obtained with postoperative radiotherapy regimens.

CONCLUSION

Preoperative radiotherapy of the operative site applied within 4 h prior to elective hip surgery and total hip arthroplasty appears to be equally effective to currently accepted postoperative radiotherapy regimens in prevention of clinically significant heterotopic ossification about the hip. Improved patient comfort, ease of treatment management, and avoidance of possible postoperative complications associated with moving and positioning the patient in the immediate postoperative period are the major advantages of the preoperative radiotherapy concept.