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[Collagens and growth factors in heterotopic ossification].

Heterotopic Ossification (HO) occurs as a consequence of several diseases and of various forms of trauma. HO is particularly frequent in paraplegic patients with spinal cord lesions. It is obvious that extraskeletal cells are able to differentiate into an osteogenic direction. However, the mechanisms of the induction process of HO and the stimulating agents are not precisely known. A novel tool for studying the ossification process at the level of transcription is the technique of non-radioactive in situ hybridisation. Using digoxigenin labeled cDNA probes we investigated the distribution patterns of types I, II and III collagen mRNAs and the mRNA of Transforming Growth Factor beta 1 (TGF-beta 1) in heterotopic ossification of pressure sores of paraplegic patients. The three collagen mRNAs as well as the TGF-beta 1 mRNA exhibited substantially divergent distribution patterns. Type I (alpha 1) collagen mRNA was predominantly detectable in preosteoblasts, chondroblasts and chondrocytes of the ossification zone. Type II (alpha 1) collagen mRNA was nearly exclusively found in cells of the chondrogenic lineage. Type III (alpha 1) collagen mRNA was detectable at low levels in soft tissue, but was strongly expressed by chondroblasts and chondrocytes of heterotopic cartilage. In contrast expression of TGF-beta 1 mRNA was found in a spatial different distribution pattern in areas of proliferation of mesenchymal tissue and in different stages of ectopic bone formation. As in the case of collagen Type I (alpha 1) and III (alpha 1) mRNAs the maximum of localization of TGF-beta 1 was detected in chondroblastic areas of heterotopic ossification. Taken together our in situ hybridization experiments provide evidence that chondrogenic cells play a central role in the process of HO with a phenotypic alteration in collagen type expression and a strong expression of TGF-beta 1 mRNA. These findings support individual in vivo function for TGF-beta 1 in local cellular regulation of ectopic bone formation.

Cartilage↗

Rofecoxib inhibits heterotopic ossification after total hip arthroplasty.

INTRODUCTION: Nonsteroidal anti-inflammatory drugs (NSAIDs) prevent heterotopic ossification but gastrointestinal complaints are frequently. Selective cyclooxygenase-2 (COX-2) inhibiting NSAID produce less gastrointestinal side effects. PATIENTS AND METHODS: A prospective two-stage study design for phase 2 clinical trials with 42 patients was used to determine if rofecoxib (a COX-2 inhibitor) 50 mg oral for 7 days prevents heterotopic ossification. A cemented primary THA was inserted for osteoarthroses. After 6 months heterotopic bone formation was assessed on AP radiographs using the Brooker classification. RESULTS: No heterotopic ossification was found in 81% of the patients, 19% of the patients had Brooker grade 1 ossification. CONCLUSION: Using a two-stage study design for phase 2 clinical trials, a 7-day treatment of a COX-2 inhibitor (rofecoxib) prevents effectively the formation of heterotopic ossification after cemented primary total hip arthroplasty.

Adult↗

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.

Adult↗

[Treatment of heterotopic ossification by extracorporeal shock wave: 26 patients].

OBJECTIVES: To evaluate the effects of extracorporeal shockwave therapy (ESWT) on heterotopic ossification leading to functional limitations in the short and medium term. METHODS: Twenty-six patients with heterotopic ossification received sessions of ESTW (4000 shocks, 3/s), with an energy ranging from 0.54 to 1.06 mJ/mm2, once a week for 4 consecutive weeks. Intermediary assessments performed 1 month after the last session related to pain (on a visual analog scale [VAS]), range of motion, functional independence (FIM), walking distance (whenever possible), radiology, and blood calcium and alkaline phosphatase levels. Eighteen patients with total hip arthroplasty (THA) were followed up by quiz, at 11 months, on average. RESULTS: Heterotopic ossification was neurogenic in 5 patients and nonneurogenic in 21. The length of evolution of ossification was 32+/-21 months. The measurements showing significant improvement in the short term were pain, with a mean decrease of 4.32 to 1.14 on a VAS; joint flexion, with an mean increase of 8.18+/-11.9 degrees; and walking distance, with a mean increase from 1126 to 2776 m. The treatment was tolerated for the most part. THA cases showed a decline in factors initially shown to be improved. However, the long-term results were superior to clinical status before treatment. CONCLUSION: ESWT might be an interesting treatment for heterotopic ossification and can be a complement to usual medical treatment, physiotherapy, and before surgery.

Adolescent↗

Randomized trial comparing early postoperative irradiation vs. the use of nonsteroidal antiinflammatory drugs for prevention of heterotopic ossification following prosthetic total hip replacement.

PURPOSE: A randomized trial was undertaken to assess the comparative efficacy of early postoperative irradiation with either 5 or 7 Gy vs. the use of nonsteroidal antiinflammatory drug (NSAID) for prevention of heterotopic ossification (HO) following prosthetic total hip replacement (THP). METHODS AND MATERIALS: Between 1993 and 1994, 301 patients were randomized to receive postoperative irradiation (5 or 7 Gy) or NSAID. One hundred and thirteen patients were treated with NSAID (indomethacin 2 x 50 mg/day for 1 week), 93 patients were irradiated with a single 7 Gy fraction, 95 patients with a single 5 Gy fraction. The treatment volume included the soft tissues between the periacetabular region of pelvis and the intertrochanteric portion of the femur. X-rays of treated hips were obtained immediately and 6 months after surgery. Heterotopic ossification was scored according to the Brooker Grading system. One hundred patients receiving no prophylactic therapy after total hip arthroplasty between 1988 and 1992, were analyzed and defined as historical control group. RESULTS: Incidence of heterotopic ossification was 16.0% in NSAID-group (Brooker Score I: 8.0%; II: 6.2%; III: 1.8%; IV: 0%), 30.1% in 5 Gy group (Brooker Score I: 24.7%; II: 4.3%; III: 1.1%; IV: 0%), and 11.1% in 7 Gy group (Brooker Score I: 11.6%; II: 0%; III: 0%; IV: 0%). Regarding overall heterotopic ossification there was a significant difference between the NSAID group and the 5 Gy group (p < .015), respectively, between the 7 Gy group and the 5 Gy group (p < .0001). No significant difference was noted in the influence of overall HO between the NSAID and the 7 Gy group (p > 0.3). Analyzing the clinically significant HO (Brooker Score III and IV) patients irradiated with 7 Gy developed less HO than those treated with NSAID (p = 0.003). Incidence of HO was greater in the untreated historical control group (Brooker Score I: 26%; II: 15%; III: 19%; IV: 5%) than in all three prophylacticly treated groups. CONCLUSION: Prophylactic irradiation of the operative site after hip replacement with single a 7 Gy fraction is the most effective postoperative treatment schedule in prevention of clinically significant heterotopic ossification. This therapy modality is more effective than irradiation with a single 5 Gy fraction or use of NSAID.

Aged↗

The suppression of heterotopic ossifications: radiation versus NSAID therapy--a prospective study.

This prospective, randomized study compares the effect of postoperative irradiation and nonsteroidal anti-inflammatory drug (NSAID) therapy on the prevention of heterotopic ossifications after the implantation of a total hip endoprosthesis. A total of 154 operations were performed; one group of patients underwent radiation treatment of 3 x 3.3 Gy, and the other group took 3 x 50 mg of diclofenac per day over a period of 3 weeks. Average age, sex, preoperative diagnosis, and risk factors were similar in both groups. Postoperative radiation began on average 2.9 days after operation, and the radiation therapy was finished on average within 3.8 days. NSAID prophylaxis was begun on the first postoperative day. Heterotopic ossifications occurred in two of the patients who had undergone postoperative prophylaxis by radiation. In both cases, the ossification was Brooker I, and there was no functional impairment. There were no ossifications of Brooker II-IV in this group. One patient had a Staphylococcus epidermidis infection, and fistula revision had to be carried out; the prosthesis could be left in place. In the group treated with NSAID, 16 heterotopic ossifications stage Brooker I and 2 stage Brooker II could be detected. Eleven patients stopped the treatment because of gastrointestinal problems. Both postoperative radiation and NSAID therapy have proved to be effective prophylactic methods. In direct comparison, radiation prophylaxis by 3 x 3.3 Gy proved to be slightly more successful than NSAID prophylaxis.

Anti-Inflammatory Agents, Non-Steroidal↗

Meniscal ossification in spontaneous osteoarthritis in the guinea-pig.

OBJECTIVE: The purpose of this study was to evaluate the ossification state of the meniscus in the guinea-pig stifle joint using micro-computerized tomography. DESIGN: Hind limbs from six (N=12) and 24 (N=11) month-old male Hartley guinea-pigs were removed and the joints were imaged using high resolution micro-computerized tomography. The ossified volume of the medial and lateral menisci from both groups of animals was quantified. RESULTS: Ossification of both the medial and lateral menisci of the both the 6- and 24-month-old animals was observed. In both age groups, the ossified region of the medial meniscus was significantly larger than the lateral meniscus. In addition, there is a significant increase in ossified volume of the medial meniscus between 6 and 24 months of age. CONCLUSIONS: There is a significant amount of ossification of the menisci in the male Hartley guinea-pig, with the medial compartment showing more bone than the lateral. In addition, as the animals age, there is an increase in ossification within the medial compartment. Bone remodeling and cartilage degeneration is evident in the medial compartment within these animals as they age. It is possible that the increased ossification of the medial meniscus could alter the joint biomechanics and, in part, stimulate this medial compartment joint destruction.

Aging↗

[Long-term results after acetabular fractures with respect to heterotopic ossifications].

BACKGROUND: Arthrosis, necrosis of the femoral head and heterotopic ossification (HO) tend to decline the outcome of acetabular fractures despite of good fracture reduction. In this study functional outcome and degree of HO were analyzed due to fracture type and surgical approach. The aim of this study is to delineate wether minimization of soft tissue damage increases the functional outcome. PATIENTS AND METHODS: 55 patients with surgically treated acetabular fractures (mean age: 40.4 (20-81) years, male 43, female 12) where retrospectively evaluated with a mean follow-up of 7.7 (4.4-12.3) years. Fractures were classified according to the Orthopaedic Trauma Association (OTA), functional outcome was scored by D'Aubigné-Postel and the degree of HO was defined by Brooker's classification. RESULTS: Following the OTA the distribution of fractures was: A-24 (44 %), B-23 (42 %) and C-8 (15 %). Mean D'Aubigné Index (max. 18 points) was 15.2, distributed to fracture type: A-15.9, B-15.0 and C-13.6. 32 % of all heterotopic ossifications were classified as Brooker 0, 10 % as Brooker 1, 29 % as Brooker 2 and Brooker 3 each, whereas Brooker 4 ossifications were not observed. 2/3 of the severe ossifications were observed using extended approaches or in case of type C fractures. The iliofemoral approach showed the tendency of fewer ossifications compared to extended approaches. CONCLUSION: Decrease of soft tissue damage during acetabular surgery plays an important role to improve outcome. Due to the higher risk of wrong implant position and insufficient reduction using a soft tissue sparing approach, we recommend a CT scan postoperatively to evaluate reduction and osteosynthesis.

Acetabulum↗

[Prevention of periarticular ossification--with results of a randomized, double-blind study comparing acemetacin versus indomethacin].

We examined the effect of NSAR in the prophylaxis of heterotopic ossifications after hip arthroplasty. During a randomized doubleblind study 59 patients took Indometacin and 60 patients Acemetacin for three weeks after the operation. All of them got a thrombosis prophylaxis with Heparin and a short term antibiotic prophylaxis. The range of ossifications was checked three months after the operation according to Arcq. The proportion of patients with no clinical symptoms (grade 0 or 1) was 92.3% in the indometacin group and 98.2% in the acemetacin group. Because of side effects (mainly gastrointestinal) 7 patients (11.9%) in the indometacin group and 5 patients (8.3%) in the acemetacin group stopped the study. In a previous study we had examined the effect of thrombosis prophylaxis by Heparin on the heterotopic ossifications. These results could now be taken for comparison. According to these results the examined NSAR Indometacin and Acemetacin raised the group of low grade heterotopic ossifications. The higher grades (2 degrees and 3 degrees according to Arcq) were only be seen in less than 5%. That is why we recommend the NSAR (Acemetacin or Indometacin) generally after hip arthroplasty as prophylaxis of heterotopic ossifications.

Adult↗

[Does the type of prosthesis have an effect on the development of periarticular ossification?].

We checked up the hip operations that were done by the same surgeon in the years 1974-76 and 1984-86. For this examination we had 115 Müller Charnley prosthesis and 75 anatomically straight stems type SF. The heterotopic ossifications were classified according to Arcq. The aim was to find out if the form and type of the femoral stem, the changing of the leg length and of the CCD-angle, the post operative CCD-angle and the number of blood transfusion influences the dimension of heterotopic ossifications. The groups with higher amount of periarticular ossification (Arcq grade 2 and 3) are generally smaller. In the case of SF prostheses the ossifications raised when the CCD angle difference also raised. But the Müller/Charnley prostheses showed quite the contrary. Though there was no significance in this manner. Although in the other controlled factors there were no significant differences. The difference that was found between the two types of prosthesis was equalized with another factor: Low-dose heparin. This was the only significant influence on heterotopic ossification.

Aged↗

[Suppression of heterotopic ossification: single-dose versus fractionated irradiation--animal study].

Periarticular ossification is one of the main problems of total hip replacement. Irradiation with megavolt photons is known to be a well recognized means of prevention of heterotopic ossification. So far only little scientific basis exists about the most favourable way of radiotherapy for prevention of ectopic ossification. In this study two theoretically equivalent doses are compared. Allogeneic bone matrix was implanted into both thighs of 50 adult male Wistar rats for experimental induction of heterotopic ossification. Immediately after operation the thigh implants were irradiated with a single dose of 7 Gy or a total dose of 10 Gy given in 5 fractions of 2 Gy each. In the model of matrix-induced osteogenesis in rats fractionated irradiation by 5 x 2 Gy leaded to a highly-significant (p = 0.001) better suppression of ectopic ossification compared to irradiation by 1 x 7 Gy. Once-only irradiation with 1 x 7 Gy leads to a reduction of the calcium contents by 27.5%, split irradiation by 5 x 2 Gy obtained a reduction by 66.9% compared to the calcium contents of thigh implants not exposed to radiation. In view of experimentally proven better effects, fractionated irradiation has to be preferred to single dose radiation also considering less side effects in split radiation.

Animals↗

Ossification of eustachian tube cartilage and Ostmann's fatty tissue in chronic renal failure.

Ossification of the eustachian tube (ET) cartilage in 2 cases of chronic renal failure is reported for the first time. In both cases, the ossification was observed in the medial lamina of the ET cartilage. In addition, ossification of Ostmann's fatty tissue was observed in case 1, and ossification of the lateral lamina of the ET cartilage was seen in case 2. Correlation between ossification in chronic renal failure and dysfunction of the ET caused by ossified ET cartilage and Ostmann's fatty tissue is discussed.

Adipose Tissue↗

Basal cell carcinoma with massive ossification.

We report a case of basal cell carcinoma with massive ossification in a 66-year-old white man. Ossification in various benign and malignant neoplasms have been reported including basal cell carcinomas, in which ossifications are seen in small foci or peripheral rim of the tumor. However, in our case, massive ossification is seen throughout the tumor, and only small areas of the periphery of the tumor show diagnostic histology. Therefore, this case might have presented a diagnostic difficulty or been misdiagnosed as an osteoma cutis if a smaller incisional or punch biopsy had been performed. The phenomenon of bone formation itself is not specific for any diagnostic entity, and therefore an underlying lesion should be carefully sought in case of secondary ossification.

Aged↗

Roentgenographic evaluation of ossification and calcification of the lumbar spinal canal after intradiscal betamethasone injection.

There have been reports of lumbar spinal canal ossification and calcification after triamcinolone intradiscal injection therapy. Our objective was to observe the roentgenographic changes after betamethasone intradiscal injection therapy for lumbar disc diseases. The subjects were 183 patients (498 discs; 130 men and 53 women) who underwent discography and betamethasone intradiscal injection therapy and were followed for a mean of 5 years and 7 months. Ossification and calcification appeared de novo (three patients, three discs) or enlarged (four patients, five discs) in the outer layer of the posterior annulus fibrosus or posterior longitudinal ligament in eight discs among seven patients (3.8%). The incidence and degree of ossification and calcification in our patients were significantly lower than those reported in previous studies, and a long time elapsed before ossification and calcification appeared or enlarged. Intradiscal injection of betamethasone did not appear to confer any incremental relative risk for lumbar spinal canal ossification and calcification based on review of follow-up roentgenographs.

Adolescent↗

Immunohistochemical demonstration of bone morphogenetic protein-2 and transforming growth factor-beta in the ossification of the posterior longitudinal ligament of the cervical spine.

To clarify the mechanism of ossification of the posterior longitudinal ligament, immunohistochemical localization of bone morphogenetic protein-2 and transforming growth factor-beta was examined using surgical specimens of ligament tissues from an affected patient. Two polyclonal antibone morphogenetic protein-2 antibodies and an anti-human transforming growth factor-beta antibody were used as primary antibodies. Bone morphogenetic protein-2 and transforming growth factor-beta were present in ossified matrix and chondrocytes of adjacent cartilaginous areas of ossification of the posterior longitudinal ligament. Although immunostaining with antibone morphogenetic protein-2 antibodies also was observed in mesenchymal cells with fibroblastic features in the immediate vicinity of the cartilaginous areas, no staining could be detected with anti-human transforming growth factor-beta antibody in these cells. The presence of these factors were specific for the ossified ligament because no immunostaining was observed after using antibodies in the posterior longitudinal ligament at unossified levels from the same patient. It is suggested that bone morphogenetic protein-2 and transforming growth factor-beta play important roles in the development of ossification of the posterior longitudinal ligament and that bone morphogenetic protein-2 may act as an initiating factor in the development of ossification of the posterior longitudinal ligament by stimulating differentiation of mesenchymal progenitor cells. Transforming growth factor-beta may stimulate bone formation at a later stage of the process of ectopic ossification.

Aged↗

Myelopathy caused by ossification of ligamentum flavum.

STUDY DESIGN: Retrospective study of seven cases of ossification of ligamentum flavum from two urban hospitals in a Chinese population. OBJECTIVES: To inspect the epidemiology, clinical presentation, pathology, and treatment outcome in these Chinese patients with ossification of ligamentum flavum. SUMMARY OF BACKGROUND DATA: Ossification of ligamentum flavum involving the lower thoracic region is relatively common in the Japanese population. It is usually presented with myelopathy of progressive nature. MATERIALS AND METHODS: Five patients were male and two were female. The mean age was 52 years (range 41-73 years). Diagnosis was made by CT scan, MRI, and subsequent histology. Six patients have been treated by laminectomy and one by laminoplasty. The average follow-up duration is 34 months (range 26-44 months). The outcome is evaluated by Japanese Orthopaedics Association (JOA) score. RESULTS: The average time of presentation from the onset of symptoms was 9 months (range 3-12 months). Most of the patients presented with lower limb numbness and gait disturbance. One case was presented after a minor trauma. Mean JOA score was 4.8 (range 2-7, of 11). The lower thoracic level was the most frequently involved region. One case was associated with ossification of the posterior longitudinal ligament. Two patients had transient postoperative neurologic deterioration, which improved subsequently. Mean percentage of recovery after surgery in terms of JOA score is 65% (25-100%), with a mean final JOA score of 7.8. CONCLUSION: Ossification of ligamentum flavum is an uncommon cause of myelopathy in the Chinese population. It can present acutely after minor trauma. Posterior decompression, especially with en bloc dissection of laminae, gives satisfactory results.

Adult↗

Occupational recovery after open-door type laminoplasty for patients with ossification of the posterior longitudinal ligament.

STUDY DESIGN: A cross-sectional survey of occupational recovery after surgery with patients who had ossification of the posterior longitudinal ligament. OBJECTIVES: To evaluate occupational recovery after open-door type laminoplasty for patients with ossification of the posterior longitudinal ligament. SUMMARY OF BACKGROUND DATA: The literature contains numerous reports on the surgical results of laminoplasty for ossification of the posterior longitudinal ligament, but very few reports are available on postoperative quality of life, and even fewer on occupational recovery after laminoplasty. METHODS: A cross-sectional survey was conducted of 301 patients with ossification of the posterior longitudinal ligament in the cervical spine who were employed before open-door type laminoplasty. Presurgical occupations were classified into three categories: light sedentary labor, light standing labor, and heavy labor. High-rise workers and professional drivers were analyzed separately. The subjects were rated by occupational category for determining the occupational recovery ratio. Factors analyzed for impact on recovery were pre- and postsurgery severity of myelopathy, duration of myelopathy, age at surgery, gender, and type of ossification of the posterior longitudinal ligament. RESULTS: Of the 301 patients studied, 160 (53%) returned to work. Poor recovery rates were observed for heavy labor, high-rise workers, and professional drivers. The period required for return to work did not significantly differ among occupational categories. Occupation, presurgery severity of myelopathy, and postsurgery severity of myelopathy were significantly correlated with occupational recovery. CONCLUSION: Patients' occupations should be carefully considered when designing postsurgery occupational rehabilitation programs, and patients should receive postoperative advice regarding the suitability of occupation.

Cross-Sectional Studies↗

Foreign body giant cell reactions and ossification associated with benign melanocytic naevi.

AIMS: To assess the incidence of foreign body giant cell reactions and ossification in benign/melanocytic naevi; and to examine their pathological features to gain an insight into their pathogenesis. METHODS: Intradermal (n = 185) and compound naevi (n = 110) from a routine histology service, together with 60 naevi submitted to an ophthalmic pathologist, were examined for foreign body reactions and ossification. Additional cases were identified prospectively in the course of routine reporting. The clinical and pathological features of positive cases were assessed. RESULTS: Foreign body reactions were identified in nine (4.9%) intradermal and four (3.6%) compound naevi, but in none of the naevi from around the eye. One intradermal naevus showed ossification. A further 11 naevi showing foreign body reaction and five showing ossification alone were identified prospectively. The 24 naevi showing a foreign body reaction had a similar age and sex distribution to controls but were more likely to occur on the head and neck. The reaction usually occurred deep to the naevus, sometimes in relation to a hair follicle, and fragments of hair or keratin were identified in most. Osteoid or bone was present within the reaction in five. In six other naevi, all from the head and neck of women, osteoid or mature bone was present deep to the naevus in the absence of a giant cell reaction. CONCLUSIONS: Foreign body giant cell reactions occur not uncommonly in relation to benign naevi, as a result of follicular damage, possibly due to trauma. The similar siting of foci of bone suggests that ossification occurs as a secondary phenomenon in these cases.

Adult↗