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Competing Interests: The author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE conflict of interest forms for authors and Clinical Orthopaedics and Related Research ® editors and board members are on file with the publication and can be viewed on request.

Background: Fibrodysplasia ossificans progressiva (FOP) is an ultrarare genetic disorder with episodic and progressive heterotopic ossification. Tissue trauma is a major risk factor for flareups, heterotopic ossification (HO), and loss of mobility in patients with FOP. The International Clinical Council on FOP generally recommends avoiding surgery in patients with FOP unless the situation is life-threatening, because soft tissue injury can trigger an FOP flareup. Surprisingly little is known about flareups, HO formation, and loss of mobility after fractures of the normotopic (occurring in the normal place, distinct from heterotopic) skeleton when treated nonoperatively in patients with FOP., Questions/purposes: (1) What proportion of fractures had radiographic evidence of union (defined as radiographic evidence of healing at 6 weeks) or nonunion (defined as the radiographic absence of a bridging callus at 3 years after the fracture)? (2) What proportion of patients had clinical symptoms of an FOP flareup because of the fracture (defined by increased pain or swelling at the fracture site within several days after closed immobilization)? (3) What proportion of patients with fractures had radiographic evidence of HO? (4) What proportion of patients lost movement after a fracture?, Methods: We retrospectively identified 36 patients with FOP from five continents who sustained 48 fractures of the normotopic skeleton from January 2001 to February 2021, who were treated nonoperatively, and who were followed for a minimum of 18 months after the fracture and for as long as 20 years, depending on when they sustained their fracture during the study period. Five patients (seven fractures) were excluded from the analysis to minimize cotreatment bias because these patients were enrolled in palovarotene clinical trials (NCT02190747 and NCT03312634) at the time of their fractures. Thus, we analyzed 31 patients (13 male, 18 female, median age 22 years, range 5 to 57 years) who sustained 41 fractures of the normotopic skeleton that were treated nonoperatively. Patients were analyzed at a median follow-up of 6 years (range 18 months to 20 years), and none was lost to follow-up. Clinical records for each patient were reviewed by the referring physician-author and the following data for each fracture were recorded: biological sex, ACVR1 gene pathogenic variant, age at the time of fracture, fracture mechanism, fracture location, initial treatment modality, prednisone use at the time of the fracture as indicated in the FOP Treatment Guidelines for flare prevention (2 mg/kg once daily for 4 days), patient-reported flareups (episodic inflammatory lesions of muscle and deep soft connective tissue characterized variably by swelling, escalating pain, stiffness, and immobility) after the fracture, follow-up radiographs of the fracture if available, HO formation (yes or no) as a result of the fracture determined at a minimum of 6 weeks after the fracture, and patient-reported loss of motion at least 6 months after and as long as 20 years after the fracture. Postfracture radiographs were available in 76% (31 of 41) of fractures in 25 patients and were independently reviewed by the referring physician-author and senior author for radiographic criteria of fracture healing and HO., Results: Radiographic healing was noted in 97% (30 of 31) of fractures at 6 weeks after the incident fracture. Painless nonunion was noted in one patient who sustained a displaced patellar fracture and HO. In seven percent (three of 41) of fractures, patients reported increased pain or swelling at or near the fracture site within several days after fracture immobilization that likely indicated a site-specific FOP flareup. The same three patients reported a residual loss of motion 1 year after the fracture compared with their prefracture status. HO developed in 10% (three of 31) of the fractures for which follow-up radiographs were available. Patient-reported loss of motion occurred in 10% (four of 41) of fractures. Two of the four patients reported noticeable loss of motion and the other two patients reported that the joint was completely immobile (ankylosis)., Conclusion: Most fractures treated nonoperatively in individuals with FOP healed with few flareups, little or no HO, and preservation of mobility, suggesting an uncoupling of fracture repair and HO, which are two inflammation-induced processes of endochondral ossification. These findings underscore the importance of considering nonoperative treatment for fractures in individuals with FOP. Physicians who treat fractures in patients with FOP should consult with a member of the International Clinical Council listed in the FOP Treatment Guidelines ( https://www.iccfop.org )., Level of Evidence: Level IV, therapeutic study., Competing Interests: All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research ® editors and board members are on file with the publication and can be viewed on request., (Copyright © 2023 by the Association of Bone and Joint Surgeons.)

Competing Interests: All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request. The author certifies that neither he, nor any members of his immediate family, has funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article.

Background: Heterotopic ossification (HO) is common after total joint arthroplasty and usually does not cause diagnostic problems. However, the occurrence of HO after oncologic prostheses implantation can be troublesome as it may mimic a locally recurrent tumor. Because this distinction could have a profound impact on the surgeon and patient, it is important to distinguish the two entities; to our knowledge, no study has evaluated this after oncologic endoprosthetic reconstruction around the knee after tumor resection., Questions/purposes: (1) How common is the occurrence of HO compared with local recurrence (LR) after resection of bone sarcoma and the use of an oncologic knee prosthesis? (2) Are there any factors associated with the development of HO after limb salvage procedures with an endoprosthesis? (3) What features allow the surgeon to differentiate HO from a locally recurrent tumor in this setting?, Methods: Between 2002 and 2018, we performed 409 resections of primary bone tumors followed by reconstructions with oncologic endoprostheses. Of these, 17% (71 of 409) died before 2 years and did not have HO at that time, 2% (8 of 409) were lost to follow-up before 2 years, and another 2% (10 of 409) did not have radiographs available at a minimum of 2 years after surgery (and had not developed HO before then), and so could not be analyzed, leaving 320 patients for analysis in this retrospective study. Forty-two patients were excluded; 2% (5 of 320) for a history of failed allograft reconstruction, 3% (8 of 320) for pathologic fracture at presentation, 2% (6 of 320) for inadequate or complicated biopsy, 1% (2 of 320) for stem fractures, 2% (7 of 320) for stem loosening, and 4% (14 of 320) for extracortical bone bridging, leaving 278 patients for final evaluation. Two observers analyzed AP and lateral radiographs for signs of HO at a mean follow-up of 63 ± 33 months after surgery. We defined HO as extraskeletal bone formation in soft tissues. The primary study endpoint was survivorship free from HO, as ascertained by a competing-risks estimator. To identify factors associated with HO appearance, the demographic, radiographic, clinical, pathologic, and surgical characteristics were compared between patients with HO and those who had no lesion. Characteristic features were also compared between patients with HO and those with LR to help their differentiation. Univariate analysis was used for all statistical evaluations., Results: HO developed in 8% (21 of 278) of patients in whom oncologic knee prosthesis was implanted. LR developed in 10% (28 of 278) of the patients. According to survivorship estimates, the HO-free survival rate was not different from the LR-free survival rate at 2 years after oncologic knee reconstruction (76 ± 5% [95% CI 63 to 87] versus 74 ± 5% [95% CI 62 to 88]; p = 0.19). History of infection was more common in patients with HO than in patients with no lesion (19% [4 of 21] versus 5% [12 of 229], Odds ratio [OR] 6 [95% CI 2 to 17]; p < 0.001). The male sex was more common in the HO group as well (76% [16 of 21] versus 55% [128 of 229], OR 2 [95% CI 1 to 5]; p = 0.03). The Modular Universal Tumor and Revision System prosthesis was more frequently used in patients with HO (67% [14 of 21]) compared to those with no lesions (40% [92 of 229]; OR 2 [95% CI 1 to 5]; p = 0.02). The lesion border in radiographs was ill-defined in 19% (4 of 21) of patients with HO and 100% (28 of 28) of patients with LR (OR 8 [95% CI 3 to 20]; p < 0.001). The median time to the appearance of HO was shorter than the time to LR (8 months [3 to 13] versus 16 months [11 to 21], [95% CI 10 to 13]; p < 0.001). Pain at presentation was more frequent in patients with LR than in those with HO (86% [24 of 28] versus 14% [3 of 21], OR 36 [95% CI 7 to 181]; p < 0.001)., Conclusion: HO may occur after the use of oncologic knee prostheses for reconstruction after tumor resection. In most patients, HO could be differentiated from local recurrence through identifying a well-defined border on radiographs. Otherwise, factors such as an earlier time of presentation and absence of pain could suggest an HO, rather than an LR., Level of Evidence: Level III, therapeutic study., Competing Interests: All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request. The authors certify that neither they, nor any members of their immediate families, have funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article., (Copyright © 2020 by the Association of Bone and Joint Surgeons.)

Background: Although use of nonsteroidal antiinflammatory drugs and low-dose irradiation has demonstrated efficacy in preventing heterotopic ossification (HO) after THA and surgical treatment of acetabular fractures, these modalities have not been assessed after traumatic blast amputations where HO is a common complication that can arise in the residual limb., Questions/purposes: The purpose of this study was to investigate the effectiveness of indomethacin and irradiation in preventing HO induced by high-energy blast trauma in a rat model., Methods: Thirty-six Sprague-Dawley rats underwent hind limb blast amputation with a submerged explosive under water followed by irrigation and primary wound closure. One group (n = 12) received oral indomethacin for 10 days starting on postoperative Day 1. Another group (n = 12) received a single dose of 8 Gy irradiation to the residual limb on postoperative Day 3. A control group (n = 12) did not receive either. Wound healing and clinical course were monitored in all animals until euthanasia at 24 weeks. Serial radiographs were taken immediately postoperatively, at 10 days, and every 4 weeks thereafter to monitor the time course of ectopic bone formation until euthanasia. Five independent graders evaluated the 24-week radiographs to quantitatively assess severity and qualitatively assess the pattern of HO using a modified Potter scale from 0 to 3. Assessment of grading reproducibility yielded a Fleiss statistic of 0.41 and 0.37 for severity and type, respectively. By extrapolation from human clinical trials, a minimum clinically important difference in HO severity was empirically determined to be two full grades or progression of absolute grade to the most severe., Results: We found no differences in mean HO severity scores among the three study groups (indomethacin 0.90 ± 0.46 [95% confidence interval {CI}, 0.60-1.19]; radiation 1.34 ± 0.59 [95% CI, 0.95-1.74]; control 0.95 ± 0.55 [95% CI, 0.60-1.30]; p = 0.100). For qualitative HO type scores, the radiation group had a higher HO type than both indomethacin and controls, but indomethacin was no different than controls (indomethacin 1.08 ± 0.66 [95% CI, 0.67-1.50]; radiation 1.89 ± 0.76 [95% CI, 1.38-2.40]; control 1.10 ± 0.62 [95% CI, 0.70-1.50]; p = 0.013). The lower bound of the 95% CI on mean severity in the indomethacin group and the upper bound of the radiation group barely spanned a full grade and involved only numeric grades < 2, suggesting that even if a small difference in severity could be detected, it would be less than our a priori-defined minimum clinically important difference and any differences that might be present are unlikely to be clinically meaningful., Conclusions: This work unexpectedly demonstrated that, compared with controls, indomethacin and irradiation provide no effective prophylaxis against HO in the residual limb after high-energy blast amputation in a rat model. Such an observation is contrary to the civilian experience and may be potentially explained by either a different pathogenesis for blast-induced HO or a stimulus that overwhelms conventional regimens used to prevent HO in the civilian population., Clinical Relevance: HO in the residual limb after high-energy traumatic blast amputation will likely require novel approaches for prevention and management.

Background: Short-term muscle atrophy induced by botulinum toxin A (BTxA) has been observed to impair osteogenesis in a rat closed femur fracture model. However, it is unclear whether the underlying mechanism is a direct effect of BTxA on muscle-bone interactions or an indirect effect that is driven by skeletal unloading. Because skeletal trauma in the closed fracture model also leads to disuse atrophy, we sought to mitigate this confounding variable by examining BTxA effects on muscle-bone interactions in two complementary in vivo models in which osteogenesis is induced in the absence of skeletal unloading. The overall aim of this study was to identify a potential strategy to inhibit pathological bone formation and heterotopic ossification (HO)., Questions/purposes: (1) Does muscle paralysis inhibit periosteal osteogenesis induced by a transcortical defect? (2) Does muscle paralysis inhibit heterotopic bone formation stimulated by intramuscular bone morphogenetic protein (BMP) injection?, Methods: Focal osteogenesis was induced in the right hindlimb of mice through surgical initiation of a small transcortical defect in the tibia (fracture callus; n = 7/group) or intramuscular injection of BMP-2 (HO lesion; n = 6/group), both in the presence/absence of adjacent calf paralysis. High-resolution micro-CT images were obtained in all experimental groups 21 days postinduction and total volume (ie, perimeter of periosteal callus or HO lesion) and bone volume (calcified tissue within the total volume) were quantified as primary outcome measures. Finally, these outcome measures were compared to determine the effect of muscle paralysis on inhibition of local osteogenesis in both studies., Results: After a transcortical defect, BTxA-treated mice showed profound inhibition of osteogenesis in the periosteal fracture callus 21 days postsurgery compared with saline-treated mice (total volume: 0.08 ± 0.06 versus 0.42 ± 0.11 mm(3), p < 0.001; bone volume: 0.07 ± 0.05 versus 0.32 ± 0.07 mm(3), p < 0.001). Similarly, BMP-2-induced HO formation was inhibited by adjacent muscle paralysis at the same time point (total volume: 1.42 ± 0.31 versus 3.42 ± 2.11 mm(3), p = 0.034; bone volume: 0.68 ± 0.18 versus 1.36 ± 0.79 mm(3), p = 0.045)., Conclusions: Our data indicate that BTxA-induced neuromuscular inhibition mitigated osteogenesis associated with both a transcortical defect and BMP-2-induced HO., Clinical Relevance: Focal neuromuscular inhibition represents a promising new approach that may lead to a new clinical intervention to mitigate trauma-induced HO, a healthcare challenge that is severely debilitating for civilian and war-wounded populations, is costly to both the patient and the healthcare system, and currently lacks effective treatments.

Background: Heterotopic ossification (HO) affects the majority of combat-related lower extremity wounds involving severe fracture and amputation. Defining the timing of early osteogenic-related genes may help identify candidate prophylactic agents and guide the timing of prophylactic therapy after blast and other combat-related extremity injuries., Questions/purposes: Using a recently developed animal model of combat-related HO, we sought to determine (1) the timing of early chondrogenesis, cartilage formation, and radiographic ectopic bone development; and (2) the early cartilage and bone-related gene and protein patterns in traumatized soft tissue., Methods: We used an established rat HO model consisting of blast exposure, controlled femur fracture, crush injury, and transfemoral amputation through the zone of injury. Postoperatively, rats were euthanized on Days 3 to 28. We assessed evidence of early ectopic bone formation by micro-CT and histology and performed proteomic and gene expression analysis., Results: All rats showed radiographic evidence of HO within 28 days. Key chondrogenic (collagen type I alpha 1 [COL1α1], p = 0.016) and osteogenic-related genes (Runt-related transcription factor 2 [RUNX-2], p = 0.029; osteoclacin [OCN], p = 0.032; phosphate-regulating neutral endopeptidase, X-linked [PHEX], p = 0.0290, and POU domain class 5 transcription factor [POU5F], p = 0.016) and proteins (Noggin [NOG], p = 0.04, OCN, p = 0.02, RUNX- 2, p = 0.04, and substance P-1 [SP-1], p = 0.01) in the injured soft tissue, normalized to the contralateral limb and/or sham-treated naïve rats, increased on Days 3 to 14 postinjury. By 14 days, foci of hypertrophic chondrocytes, hyaline cartilage, and woven bone were present in the soft tissue surrounding the amputation site., Conclusions: We found that genes that regulate early chondrogenic and osteogenic signaling and bone development (COL1α1, RUNX-2, OCN, PHEX, and POU5F1) are induced early during the tissue reparative/healing phase in a rat model simulating a combat-related extremity injury., Clinical Relevance: The ability to correlate molecular events with histologic and morphologic changes will assist researchers and clinicians to understand HO and hence formulate therapeutic interventions.

Background: Heterotopic ossification (HO) develops after nearly 2/3 of traumatic blast amputations in the contemporary battlefield. This phenomenon has potentially devastating consequences for servicemen and women and its pathophysiology warrants further investigation using a previously developed animal blast model., Questions/purposes: We asked, what is the (1) severity (quantity) and (2) type (location) of HO bone formation after a hindlimb blast amputation with two distinct blast media. We hypothesized that a more "war-relevant" blast medium could be a more accurate model and potentially intensify the development of HO., Methods: Using a Sprague-Dawley rat model, the pathophysiology of ectopic bone formation in a traumatic hindlimb blast amputation was evaluated. Twenty-four animals underwent blast amputations and closure based on a previously established experimental model. Half the amputations were subjected to blasted sand and the other 1/2 to blasted water. Serial orthogonal radiography was performed on each animal until euthanasia at 24 weeks to track the development of HO. Heterotopic bone severity and type were assessed by three independent graders at each time using a novel grading scale to assess quantity and quality of HO., Results: All animals had radiographic evidence of HO develop. No differences were observed in ectopic bone development between sand and water blasting regarding severity or type at any time. Animals that received water and sand blasting had moderate HO develop at 24 weeks (median, 2.0 and 2.5 weeks, respectively; range, 1-3 weeks; difference of medians, 0.5; p=0.67). At the time of euthanasia, 10 animals that were water blasted had Type 3 HO compared with 11 in the sand-blasted group (p=1.00)., Conclusions: Our study showed a clear development of HO after hindlimb blast amputation in a Sprague-Dawley rat model; however, no difference was observed in HO development based on the type of blast media. This suggests it is the blast mechanism that induces ectopic bone development, regardless of the blasted medium. The grading scale we developed for our animal-model study provided a reliable means of assessing HO severity and type., Clinical Relevance: We anticipate that future investigations will elucidate similarities between service members' wartime extremity injuries and the animal model used in our study, and with focused future research this model may have beneficial therapeutic implications as the pathophysiology of HO development is further understood.

Background: Prophylactic approaches to prevent heterotopic ossification after acetabular fracture surgery have included indomethacin and/or single-dose external beam radiation therapy administered after surgery. Although preoperative radiation has been used for heterotopic ossification prophylaxis in the THA population, to our knowledge, no studies have compared preoperative and postoperative radiation therapy in the acetabular fracture population., Questions/purposes: We determined whether heterotopic ossification frequency and severity were different between patients with acetabular fracture treated with prophylactic radiation therapy preoperatively and postoperatively., Methods: Between January 2002 and December 2009, we treated 320 patients with a Kocher-Langenbeck approach for acetabular fractures, of whom 50 (34%) were treated with radiation therapy preoperatively and 96 (66%) postoperatively. Thirty-four (68%) and 71 (74%), respectively, had 6-month radiographs available for review and were included. For hospital logistical reasons, patients who underwent operative treatment on a Friday or Saturday received radiation therapy preoperatively, and all others received it postoperatively. The treatment groups were comparable in terms of most demographic parameters, injury severity, and fracture patterns. Six-month postoperative radiographs were reviewed and graded according to Brooker. Followup ranged from 6 to 93 months and 6 to 97 months for the preoperative and postoperative groups, respectively. Post hoc power analysis showed our study was powered to detect a difference of 22% or more between patients with severe heterotopic ossification. Sample size calculations showed 915 subjects would be needed to detect a 5% relative difference in severe heterotopic ossification status between groups., Results: We detected no difference in heterotopic ossification frequency between the preoperative (eight of 36, 22%) and postoperative (19 of 71, 27%) groups (p=0.609). There was also no difference in heterotopic ossification severity between groups (p=0.666). Two of 36 (6%) in the preoperative group and three of 71 (4%) in the postoperative group developed clinically significant Grade III heterotopic ossification. No patients developed Grade IV heterotopic ossification., Conclusions: We found no difference in heterotopic ossification frequency or severity when comparing preoperative and postoperative radiation therapy. However, given the relatively low frequency of heterotopic ossification in this population, in particular the frequency of severe or symptomatic heterotopic ossification, the possibility of a Type II error must be considered. Larger, prospective studies are required to confirm our no-difference finding, but insofar as the result in this fracture population mirrors that of the THA population, unless our finding is disproven, we believe radiation therapy can be given either before or after surgery, as dictated by the clinical scenario., Level of Evidence: Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Background: Heterotopic ossification (HO) is a common complication of the operative treatment of acetabular fractures. Although the surgical approach has been shown to correlate with the development of ectopic bone, specific risk factors have not been elucidated., Questions/purposes: The purposes of this study were to determine specific risk factors associated with the development of severe HO and the frequency with which patients develop severe HO after acetabular fracture fixation through an isolated Kocher-Langenbeck approach., Methods: Using an institutional orthopaedic trauma database at a regional Level I trauma center, patients undergoing open treatment of acetabular fractures during the study period (January 2000 to January 2010) were identified. A review of medical records and imaging studies was performed on 508 patients who were treated by the senior author (MR) through an isolated Kocher-Langenbeck approach. During the study period, the senior author used indomethacin for HO prophylaxis in patients who had ipsilateral femur fracture treated with antegrade reamed medullary nailing or severe local soft tissue injury; 49 (10%) of the patients he treated with the Kocher-Langenbeck approach received prophylaxis, and they were excluded from this study, leaving a total of 459 patients who met inclusion criteria. Of those, 147 (29%) were lost to followup or did not have radiographs both before and at a minimum of 6 weeks (median, 1 week; range, 0-3 weeks), leaving 312 (61% of the patients treated with the Kocher-Langenbeck approach during this time) available for this analysis. Demographic data as well as information related to cause of injury, associated periacetabular findings, other system injuries, and treatment were gathered. Final followup radiographs were assessed for the presence of ectopic bone by two of the authors (TJO, AS) using the modified Brooker classification. Logistic regression was performed to identify possible predictors of development of severe ectopic bone., Results: The only predictor we identified for the development of severe HO was the need for prolonged mechanical ventilation (odds ratio, 7.1; 95% confidence interval, 2.9-17.3; p=0.001). Injury Severity Score, sex, presence of comminution, femoral head impaction, dislocation, degloving injury, debris in the joint, number of other fractures, and head and chest Abbreviated Injury Score>2 did not correlate with severe HO. Severe HO (Brooker Class III or IV) developed in 38 of 312 patients (12%)., Conclusions: Patients with prolonged mechanical ventilation might benefit from HO prophylaxis given the increased risk of developing severe HO in this patient population. However, future prospective studies need to be performed to verify this finding given the fact that a considerable number of patients were prophylactically treated in this study., Level of Evidence: Level IV, prognosticstudy. See Guidelines for Authors for a complete description of levels of evidence.

Background: After a decade of war in Iraq and Afghanistan, we have observed an increase in combat-related injury survival and a paradoxical increase in injury severity, mainly because of the effects of blasts. These severe injuries have a devastating effect on each patient's immune system resulting in massive upregulation of the systemic inflammatory response. By examining inflammatory mediators, preliminary data suggest that it may be possible to correlate complications such as wound failure and heterotopic ossification (HO) with distinct systemic and local inflammatory profiles, but this is a relatively new topic., Questions/purposes: We asked whether systemic or local markers of inflammation could be used as an objective means, independent of demographic and subjective factors, to estimate the likelihood of (1) HO and/or (2) wound failure (defined as wounds requiring surgical débridement after definitive closure, or wounds that were not closed or covered within 21 days of injury) in patients sustaining combat wounds., Methods: Two hundred combat wounded active-duty service members who sustained high-energy extremity injuries were prospectively enrolled between 2008 and 2012. Of these 200 patients, 189 had adequate followups to determine the presence or absence of HO, and 191 had adequate followups to determine the presence or absence of wound failure. In addition to injury-specific and demographic data, we quantified 24 cytokines and chemokines during each débridement. Patients were followed clinically for 6 weeks, and radiographs were obtained 3 months after definitive wound closure. Associations were investigated between these markers and wound failure or HO, while controlling for known confounders., Results: The presence of an amputation (p < 0.001; odds ratio [OR], 6.1; 95% CI. 1.63-27.2), Injury Severity Score (p = 0.002; OR, 33.2; 95% CI, 4.2-413), wound surface area (p = 0.001; OR, 1.01; 95% CI, 1.002-1.009), serum interleukin (IL)-3 (p = 0.002; OR, 2.41; 95% CI, 1.5-4.5), serum IL-12p70 (p = 0.01; OR, 0.49; 95% CI, 0.27-0.81), effluent IL-3 (p = 0.02; OR, 1.75; 95% CI, 1.2-2.9), and effluent IL-13 (p = 0.006; OR, 0.67; 95% CI, 0.50-0.87) were independently associated with HO formation. Injury Severity Score (p = 0.05; OR, 18; 95% CI, 5.1-87), wound surface area (p = 0.05; OR, 28.7; 95% CI, 1.5-1250), serum procalcitonin ([ProCT] (p = 0.03; OR, 1596; 95% CI, 5.1-1,758,613) and effluent IL-6 (p = 0.02; OR, 83; 95% CI, 2.5-5820) were independently associated with wound failure., Conclusions: We identified associations between patients' systemic and local inflammatory responses and wound-specific complications such as HO and wound failure. However, future efforts to model these data must account for their complex, time dependent, and nonlinear nature., Level of Evidence: Level II, prognostic study. See the Instructions for Authors for a complete description of levels of evidence.

Background: We previously found no reduction in heterotopic ossification (HO) rates after acetabular surgery with indomethacin compared with a placebo. We subsequently abandoned routine indomethacin therapy after acetabular surgery but questioned whether the incidence had changed using a posterior approach., Questions/purposes: We therefore determined (1) the incidence of HO after acetabular fracture surgery through a posterior approach; (2) the incidence of symptoms attributable to HO; and (3) the rate of reoperation for HO., Methods: We retrospectively reviewed the records of all 423 patients with acetabular fractures following our clinical protocol change; of these, 120 were treated with a Kocher-Langenbeck approach and included. The presence of radiographic HO was documented a minimum of 10 weeks postoperatively using the classification of Brooker et al. Symptoms and reoperations were recorded., Results: The overall incidence of radiographic HO was 47% (56 of 120 patients): 26% Class I-II 13% Class III, and 8% Class IV. Overall, 15% of patients developed symptoms; 3.3% underwent reoperations for excision of HO. There were no major differences between the incidence of moderate and severe HO in this study when compared with the indomethacin and placebo groups from the prior study., Conclusions: Our incidence of moderate and severe HO has not changed since discontinuing indomethacin. These findings support our institutional decision to abandon routine indomethacin prophylaxis after acetabular surgery. We recommend improved surgical techniques to limit damage to the abductors and improved risk stratification of patients when considering treatment options for HO prophylaxis.

Unlabelled: Bone morphogenic proteins (BMPs) are potent osteoinductive agents. Their use in fracture surgery is still being studied and the clinical indications are evolving. Heterotopic bone after BMP use in spine surgery is a known complication. While some literature describes the ability of BMP to enhance fracture healing, few articles describe complications of BMP. In tibial plateau fractures, after elevating the cartilage en mass, a subchondral void may be created in these fractures. Structural support provided by bone void-filling agents can be augmented with osteoinduction achieved by BMP. We asked whether heterotopic bone formation would occur more frequently with BMP-2 when used in tibial plateau fractures and whether BMP-2 enhanced the ability to maintain surgically restored subchondral bone integrity. Heterotopic bone developed more frequently in patients receiving BMP (10 of 17) than in patients not receiving BMP (one of 23). Four patients receiving BMP and no patients not receiving BMP underwent removal of heterotopic bone. Maintenance of subchondral bone integrity was similar without and with the use of BMP. BMP is a potent osteoinductive agent; however, when used for an off-label indication in periarticular situations, complications such as heterotopic bone are common and increase reoperation rates., Level of Evidence: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Bone morphogenetic proteins (BMPs) can induce bone formation in vivo when combined with appropriate carriers. Several materials, including animal collagens and synthetic polymers, have been evaluated as carriers for BMPs. We examined alginate, an approved biomaterial for human use, as a carrier for BMP-7. In a mouse model of ectopic bone formation, the following four carriers for recombinant human OP-1 (BMP-7) were tested: alginate crosslinked by divalent cations (DC alginate), alginate crosslinked by covalent bonds (CB alginate), Type I atelocollagen, and poly-D,L-lactic acid-polyethyleneglycol block copolymer (PLA-PEG). Discs of carrier materials (5-mm diameter) containing OP-1 (3-30 microg) were implanted beneath the fascia of the back muscles in six mice per group. These discs were recovered 3 weeks after implantation and subjected to radiographic and histologic studies. Ectopic bone formation occurred in a dose-dependent manner after the implantation of DC alginate, atelocollagen, and PLA-PEG, but occurred only at the highest dose implanted with CB alginate. Bone formation with DC alginate/OP-1 composites was equivalent to that with atelocollagen/OP-1 composites. Our data suggest DC alginate, a material free of animal products that is already approved by the FDA and other authorities, is a safe and potent carrier for OP-1. This carrier may also be applicable to various other situations in the orthopaedic field.

We report the case of a bilateral bipartite ossification center of the proximal tibia in a 15-year-old boy with a history of knee injury. The presence of the duplicated ossific centers was an incidental finding on radiography and computed tomography performed after injury. Arthroscopy showed continuous hyaline cartilage between the two ossific centers confirming the diagnosis of a developmental abnormality; however, the articular surface was depressed in the region overlying the smaller ossific center. We presume the presence of an accessory center in the posteromedial aspect of the tibial plate could be a source of instability for the corresponding capsular and meniscal structures. This is, to our knowledge, the first report of tibial bipartite epiphysis.

A consecutive series of revision total knee arthroplasties done at two centers was evaluated for the presence of heterotopic ossification on radiographs taken before and after revision using the classification system of Harwin et al. Knee Society scores were obtained preoperatively and at annual intervals postoperatively. The patients' demographics and clinical scores were correlated with the incidence and grade of heterotopic ossification. Minimum 2-year followup was obtained in 135 of 151 patients who had revision total knee arthroplasty during this period (89%). The incidence of heterotopic ossification before revision surgery was 23%, which increased to 56% at most recent followup (mean, 30 months; range, 24-48 months). The only risk factor identified for the development of heterotopic ossification was the presence of infection (76%), which was significantly higher than the 47% incidence of heterotopic ossification in patients who did not have an infection. The average postoperative Knee Society score was lower in patients with heterotopic ossification compared with patients without heterotopic ossification (129 points versus 148 points). Patients with heterotopic ossification had significantly lower functional scores particularly on stair climbing but did not have a significantly decreased range of motion. Parameters not associated with subsequent development of heterotopic ossification included gender (males), patient size (body mass index), surgical time, operative approach, or number of prior knee procedures.

The effectiveness of naproxen, indomethacin, and a placebo were compared for the prevention of heterotopic ossification after total hip arthroplasty. Eighty-four men at high risk of experiencing heterotopic ossification received randomly either naproxen 750 mg per day, indomethacin 75 mg per day, or a placebo for 6 consecutive weeks after surgery. Efficacy analysis showed that in 70% of patients treated with naproxen, in 34.8% of those treated with indomethacin, and in 15% of those treated with a placebo, no heterotopic ossification appeared on radiographs taken at 6 months. Naproxen was significantly more effective than the placebo or indomethacin in preventing the development of heterotopic ossification. Stratification into five categories, according to Brooker's classification at 6 months, showed that both drugs were equally superior to the placebo. Class III heterotopic ossification occurred only in patients who were given the placebo. The improvement in clinical criteria was comparable in the three groups, although at 6 months there was an improvement in abduction in patients treated with indomethacin compared with those treated with naproxen and the placebo. The overall tolerance was rated good by 87% of patients and 86% of physicians, with no difference between the groups. The results show that naproxen, given daily for 6 weeks, is an effective and safe medication for the prevention of heterotopic ossification after total hip replacement.

Fifty-three cases of symptomatic heterotopic ossification were evaluated after total hip arthroplasty for the specific purpose of determining the value of surgical excision without revision or other concurrent procedures. The mean followup was 3.5 years for range of motion and 7.8 years for radiographic evaluation. A statistically significant increase in range of motion was obtained for the group at final followup. The mean increase in flexion arc was 34 degrees, abduction and adduction arc was 22 degrees, and rotation arc was 21 degrees. Of the patients who underwent surgical excision of heterotopic bone solely because of pain, none had complete alleviation of symptoms. It is concluded that surgical excision of heterotopic bone results in significant improvement in functional outcome, but it cannot be expected to predictably alleviate pain. Finally, the ultimate arc of motion was better than that suggested radiographically by the Brooker classification system.

An animal model for the study of heterotopic ossification was developed and the effects of perioperative radiation were analyzed. In Phase I, New Zealand White rabbits (n = 18) underwent surgery either with or without muscle injury on each hip to establish the most reliable model in which to study heterotopic ossification. In Phase II, rabbits (n = 36) underwent either 400, 800, or 1200 cGy radiation to one hip 24 hours after bilateral hip surgery to establish a dose response relationship for postoperative radiation therapy. In Phase III, rabbits (n = 24) underwent preoperative radiation therapy (800 cGy) at 4, 16, or 24 hours preoperatively to investigate the mechanism of action and efficacy of preoperative radiation therapy. Monthly radiographs were graded by blinded observers for severity of heterotopic ossification. Mean grade, intraobserver and interobserver variability, and statistical significance were evaluated. In Phase II, 17 of 18 rabbits generated heterotopic ossification in both hips, and the mean grade of heterotopic ossification was always greater on the operative side with intentional muscle injury. Variability in the grading was considered excellent. Phase II revealed that 800 cGy was the minimal effective dose. Contrary to hypothesis, Phase III revealed an increasing grade of heterotopic ossification coinciding with a decreasing preoperative time interval, with the difference in heterotopic ossification grade with 24-hour versus 4-hour preoperative radiation being significant. The rabbit model is reliable and reproducible and closely resembles the human clinical situation after hip surgery. Preoperative and postoperative radiation effectively prevented heterotopic ossification formation. The results support the use of preoperative radiation and establish a need for additional investigation regarding the mechanism of action and timing of preoperative radiation therapy.

Fibrodysplasia (myositis) ossificans progressiva is a rare dominantly inherited disorder, in which defects in skeletal patterning particularly affecting the big toes, are associated with progressive endochondral ossification of the large striated muscles in a specific order leading to prolonged disability. A recent series of 28 patients studied for as many as 24 years exemplifies the presentation and course of this disease. Painful swelling of muscles (myositis) leading to ossification began at a mean age of 4.6 years (range, 0-16 years) initially in the neck and upper spine (in 25 subjects) and later around the hips, other major joints, and jaw. The rate and extent of disability was unrelated to the time of onset. No form of treatment produced consistent benefit. Despite the unique clinical features, the initial diagnosis of fibrodysplasia ossificans progressiva was often wrong and usually considerably delayed. Mistaken histologic diagnoses such as soft tissue sarcoma or fibromatosis could lead to inappropriate treatment.

Ossification of the posterior longitudinal ligament in the cervical spine was studied 3-dimensionally using computed tomography scans of 32 patients. The images produced were classified into 3 types based on the posterior configuration of the ossification: (1) plank shaped, (2) spindle shaped, or (3) rod shaped. Lesions with radiographically continuous and mixed type ossification on 3-dimensional computed tomography were plank shaped or spindle shaped. Rod shaped type lesions usually were radiographically segmented or showed some other type of ossification. The 3-dimensional computed tomography images change with the growth of ossification. Plank shaped type lesions appear to be the final result of ossification. Three-dimensional computed tomography scans of ossification of the longitudinal ligament are useful for decompressive surgery, providing valuable information regarding the site of concentration of compression of the spinal cord or nerve roots and the choice of surgical procedures.

A total of 237 patients with surgically treated acetabular fractures were analyzed to identify the risk factors predisposing to development of heterotopic ossification (HO) following operative treatment, and to evaluate both clinical significance of HO and the clinical outcome of operative excision of ectopic bone. All patients had a minimum of 1 year followup time. The degree of HO was determined from anteroposterior radiographs of the pelvis at the 1 year followup and was classified as Grade 0 or Grade 1 according to the amount of ectopic bone present. Forty patients (17%) who developed a moderate to severe amount of ectopic bone were classified as Grade 1. Nine who developed significant ectopic bone resulting in 20% or greater loss of hip motion underwent excision of the ectopic bone; all six available for followup showed an improvement in range of motion. A significant correlation was found between poor clinical results at the 1 year followup and Grade 1 ectopic bone formation (p < 0.001). Four factors found to highly correlate with Grade 1 ectopic bone formation were: (1) the iliofemoral surgical approach; (2) multiple (2 or more) operative findings; (3) T type fractures; and (4) the presence of associated injuries to the abdomen and chest.

To characterize the radiographic and scintigraphic features of modeling and remodeling in the heterotopic skeleton of patients who have fibrodysplasia ossificans progressiva, radiographs from 47 patients and radionuclide bone scans from 12 of those patients, all of whom had a confirmed diagnosis of the disease, were reviewed. A wide range of normal bone modeling and remodeling features was seen in the heterotopic skeleton of all but the youngest two (age, 1 year) of the 47 patients. Characteristic features of normal bone modeling identified on radiographs of the heterotopic skeleton included: (a) the development of tubular and flat bones with mature cortical and trabecular organization; (b) the presence of well defined cortical-endosteal borders enclosing medullary canals; and (c) the presence of metaphyseal funnelization in isolated ossicles or at sites of synostoses. Characteristic features of normal bone remodeling identified on radiographs of the heterotopic skeleton included: (a) the response of heterotopic bone to weight bearing stress with osteosclerosis of use and osteopenia of disuse, and (b) the resistance of heterotopic bone to fatigue failure with the absence of pathologic fractures and stress fractures. Radionuclide bone scans in 12 patients showed that remodeling of mature heterotopic bone occurred at a rate consistent with that of mature normotopic bone. This study documents the radiographic and scintigraphic features of a heterotopic skeletal system in 47 patients who have fibrodysplasia ossificans progressiva. These data provide additional support for the hypothesis that the genetic defect leading to the formation of a heterotopic skeleton involves normal skeletal morphogenesis at heterotopic sites.

Four hundred forty-seven patients with 451 displaced fractures of the femoral neck were treated with Bateman bipolar hemiarthroplasty (190 cemented and 261 uncemented) between 1985 and 1990 in the authors' institution. During a follow-up period of at least two years, the authors found less thigh pain (13% versus 46.2%) and higher Harris hip scores (86 versus 79) in the cemented group in comparison with the uncemented group. Radiographic examination showed less radiolucent zones and subsidence in the cemented group. Heterotopic ossification was more common in the cemented group. Despite the fact that the cemented group had longer operative times (average, 20 minutes) and more blood loss (average, 160 ml) during the operation, there was no significant difference in the early mortality rate observed between these two groups. The cemented prostheses provided better functional and radiographic results and fewer failures in the early stage. In addition, the cemented prostheses did not lead to more complications and higher mortality rates. Thus, for elderly patients who need early ambulation and functional recovery, the cemented Bateman bipolar prosthesis appears to be a better choice than the uncemented Bateman prosthesis.

Ectopic bone formation was associated with osteoid osteoma in the anterior rim of the acetabulum. A factor, which has been speculated to be secreted from the nidus and is responsible for increased osteoblastic activity, also seemed to have the capacity to stimulate young mesenchymal cells to differentiate into an osteogenic pathway. A case of a 35-year-old woman with osteoid osteoma, which caused ectopic ossification adjacent to the nidus, is presented.

A prospective study was completed on 106 consecutive cementless arthroplasties (94 patients) to determine the clinical and radiographic outcome. Ninety-two hips (81 patients) had complete follow-up data. The average age was 46 years, and the average follow-up period was 41 months (24-63 months). Clinically 94% had no or slight pain. Two patients had activity-limiting thigh pain. Most patients had no or slight limp and walked without support. Patients had similar outcomes regardless of their bone type. Ninety-three percent of hips were radiographically stable. Six were loose; three of those had major intraoperative fractures. Stable stems were characterized by middle and distal zone endosteal condensation and cortical hypertrophy; these occurred primarily in the distal zones for unstable implants. Calcar resorption was noted in 38% of hips with collars and in 68% without collars (p = 0.015). Endosteal erosions were seen in six hips (6.5%) and were related only to the patient's activity level (p = 0.021). Seven hips were revised, two for delayed sepsis, one for loosening after trauma, one for intraoperative fracture, and three for aseptic loosening. The Omniflex implant system provides acceptable but not outstanding results in a wide array of femoral geometries. The early difficulty with femoral fractures has been significantly reduced by using a prophylactic cerclage cable.

Sixty-six hip arthroplasties in 55 patients were reviewed to specifically study cemented versus noncemented procedures, as related to heterotopic bone formation (HBF). Other factors considered included the type of arthroplasty, surgical approaches, preoperative and postoperative medicines, preoperative predisposing diagnoses, range of motion, and pain. The overall percentage of heterotopic ossification was 64%. There was no significant difference between cemented (67%) and noncemented (55%) procedures. Except for an increased percentage (80%) of ossification after a trochanteric osteotomy, there were no significant differences between the three reviewed surgical approaches. Male osteoarthritics had the highest overall HBF. Eighty percent of patients who previously had developed HBF also did so with a contralateral hip surgery. Surprisingly, all patients with gout (100%) developed HBF. Acetylsalicylic acid used prophylactically for anticoagulation had no significant effect. Resurfacing arthroplasty procedures accounted for half of the severe grades of HBF. A decreased range of motion occurred with more severe grades of HBF.

The effect of short-term postoperative treatment with nonsteroidal antiinflammatory medication to prevent the formation of heterotopic ossification (HO) after total hip arthroplasty (THA) was studied in two groups of patients. Group A included 46 noncemented THAs in 40 men. Eight patients (13 hips) received prophylaxis with 25 mg of indomethacin three times daily for 14 days, and 32 patients (33 hips) received prophylaxis of 650 mg of aspirin twice daily for six weeks. Six to 12 months after surgery, only one hip (aspirin treated) developed HO, this being Grade I. In group B, 17 hips in 17 patients with cemented THA received prophylaxis of 25 mg of indomethacin three times daily. Of these, 12 patients were given indomethacin from one to nine days. One year after surgery, five hips had no HO and seven hips showed a Grade I or Grade II lesion. The remaining five patients in Group B received indomethacin from 19 to 26 days; one developed HO. This study demonstrated that treatment with either 650 mg of aspirin twice daily for six weeks or 25 mg of indomethacin three times daily for the first 14 postoperative days is sufficient to prevent the formation of severe HO after THA.

The formation of periarticular heterotopic bone after total hip arthroplasty is a frequent complication. The reported occurrences concerning this complication vary considerably in different reports, ranging from 15% to 90% with significant amounts in 1%-27% of the cases. Heterotopic ossification (HO) starts with the surgical operation, and the extent is well delineated on roentgenograms after six to 12 weeks. The amount of bone varies from small islands in the soft tissue to widespread bridging ossification. The cause of HO seems to be mainly related to systemic factors and is chiefly dependent on gender, diagnosis, and concurrent antiinflammatory medication. Patients at risk seem to be those with HO after a previous surgical operation, patients suffering from certain types of ankylosing spondylitis, otherwise healthy men with osteoarthrosis, patients with hypertrophic osteoarthrosis, and patients operated upon for fresh fractures or other posttraumatic conditions. The surgical technique and the local tissue trauma probably moderate both the occurrence and amount of HO. HO does not seem to cause pain or to decrease hip muscle strength but does limit hip mobility in cases with significant amount of ossification.

Heterotopic ossification at the site of insertion of an intramedullary nail was observed in five central nervous system-injured patients with femoral fractures. Three of these patients experienced a reduction in the range of motion of the ipsilateral hip joint, which in two improved with physical therapy. Patients with central nervous system injury who have closed interlocking intramedullary nail fixation may be at increased risk of heterotopic ossification at the surgical site.

Few complications from tenodesis of the long head of the biceps brachii have been described despite the wide variety of techniques. In a 53-year-old man, rupture of this tendon was treated by tenodesis and was complicated by heterotopic ossification that severely limited the function of the shoulder joints. Nonsurgical conservative treatment of biceps tendon ruptures may avoid the possibility of this complication.

The regional-development of heterotopic bone around the hip and the influence of postoperative prophylaxis with antiinflammatory drugs were studied in 66 patients treated with 74 noncemented, porous-coated total hip arthroplasties (THA) using the McFarland approach. Thirty patients (34 hips) were treated with antiinflammatory drugs during the early postoperative period. Heterotopic bone developed in two different regions: central, around the neck of the femoral component, and lateral to the greater trochanter of the femur. Central ossifications were recorded in 53% of the hips and appeared significantly less frequently in patients postoperatively treated with antiinflammatory drugs. Lateral ossifications were recorded in 71% of the hips, and no significant prophylactic effect was found for postoperative antiinflammatory treatment. In response to the McFarland approach in THA, heterotopic ossifications may appear both centrally around the neck of the femoral component and lateral to the trochanter in the substance of the medial gluteal muscle. The latter may be comparable to post-traumatic myositis ossificans.

Nine patients who had spinal cord injury and were receiving diphosphonate therapy for established neurogenic heterotopic ossification in 14 hips were followed up for an average of 14 months. Diphosphonate therapy at a dosage of 10 mg/kg/day when prescribed an average of 26 days after diagnosis did not prevent radiographically evident progression of heterotopic ossification. The interval of one to 30 days between clinical diagnosis and institution of diphosphonate treatment did not appear to affect the duration of radiographic progression or the final radiographic grade at maturity. Disodium etidronate therapy did not prevent the appearance of heterotopic ossification in three previously unaffected hips, although the final radiographic grade was mild. The radiographic progression of heterotopic ossification averaged 5.3 months. No clinically detectable side effects were attributable to the medication at the dosage prescribed after an average of 14 months of therapy. Due to the radiographic progression noted in patients who received 10 mg/kg/day, diphosphonate has been increased to dosages of 20 mg/kg for six months after early diagnosis.

While accessory ossicles are relatively common in the feet, major developmental chondro-osseous variations in otherwise normal feet appear to be extremely unusual. The "bifid os calcis" has been reported infrequently since its first description by Sever in 1930. The majority of cases are fortuitously diagnosed, usually in children three years of age or older. The current case was diagnosed shortly after birth. The most obvious roentgenographic finding was punctate ossification in the anterior portion. As in other cases, this appeared to be a solitary, bilateral variation of chondro-osseous maturation. Foot development in the fetus includes considerable variation in the development of the calcaneal ossification center and at least two examples of multiple ossification centers.

A new nuclear scanning technique was found more specific for bone, joint, and soft tissue infections than any previously described scanning technique. The leukocyte scan, whereby a patient's own cells are labeled with a radioactive tagging agent (111In oxine), can distinguish an active infectious process from other pain-inducing conditions. Ninety-seven 111In labeled autologous leukocyte scans were performed in 88 patients. The findings in 17 of 40 patients scanned for possible acute osteomyelitis, six of nine for suspected septic arthritis, and six for possible soft tissue infections, were positive. Subsequent clinical courses verified the infectious nature of these processes in all patients. Patients who had chronic osteomyelitis (14), bony metastases (four patients), heterotopic ossification (three), and degenerative arthritis (two) demonstrated negative findings. Of the seven patients scanned for acute long-bone fractures, one demonstrated positive findings. Nine scans demonstrated positive findings without determined causes. The leukocyte scan is a useful addition to the diagnostic tools of the orthopedic surgeon.

Delayed appearance of heterotopic ossification in the lumbar region occurred in a 34-year-old man with a high thoracic paraplegia. The occurrence of lumbar heterotopic ossification seems not to have been previously reported in the literature.

The effect of three weeks of postoperative treatment with indomethacin or ibuprofen on the development of periarticular heterotopic ossification (PHO) after bilateral total hip arthroplasty (THA) was investigated. Widespread PHO did not occur in 31 patients who had been treated with indomethacin or ibuprofen after both operations. Thirty-eight patients had been treated after one but not the other THA. Widespread PHO occurred in 14 of 38 untreated THA, but was not found after THA on the treated side. These findings are indicative of an inhibitory effect of nonsteroid antiinflammatory drugs on the development of PHO, since the development of severe heterotopic ossification is strongly correlated between the two sides after bilateral THA.

Ossification of the posterior longitudinal ligament of the spine (OPLL) is a newly recognized entity. As the incidence of this disease was exceptionally high in Japan, the Japanese Ministry of Public Health and Welfare instituted a special commission for the investigation of this perplexing disease; since 1975 this committee has performed an intensive study of 2100 patients with OPLL in Japan. An epidemiologic study was conducted by this group in Japan and in eastern Asiatic countries. Symptoms and disabilities caused by the disease were described. Roentgenographic findings were classified as continuous, segmental, mixed, or localized. OPLL at the thoracic and lumbar levels combined with ossification of the yellow ligament was described, and the risk of spinal cord damage as well as the importance of tomography and computerized tomographic scanning were stressed. No conclusions were reached concerning etiology, but common findings included a generalized hyperostotic tendency, a tendency for abnormal glucose metabolism, and low enteral calcium absorption. A relatively high hereditary occurrence was noted. Conservative and surgical treatment methods were described, with particular reference to spinal canal-widening operations.

Of 548 head-injured adults, 16 sustained injuries about the elbow (3%). Sixteen of 18 patients (89%) developed heterotopic ossification (HO). All elbows which had been dislocated developed new bone in the substance or adjacent to the medial or lateral collateral ligaments, or both. Some dislocations also developed significant HO in all planes. Final motion correlated with the amount of HO in the joint. Supracondylar fractures generally developed a moderate amount of anterior or posterior HO, or both. Motion was moderately compromised. Posteriorly located HO developed in olecranon fractures. Range of motion was generally functional. Ectopic bone developed in dislocations of the radial head in the area of the annular ligament, and resulted in mild to moderate loss of motion. Spasticity was not necessarily associated with the development of HO. Two tardy ulnar palsies were noticed and associated with HO in the medial collateral ligament.

Fracture care and osteogeneic response deviate significantly from normal in patients with traumatic brain injury (TBI) or spinal cord injury (SCI). In TBI open reduction and internal fixation (ORIF) are recommended whenever possible to improve mobilization in the face of spasticity and the formation of heterotopic ossification (HO). In the patient with SCI, immobility and paralysis negatively alter healing. A fracture above the level of SCI, although not altered in healing, when treated by ORIF will facilitate transfer training and self care. Lower extremity fractures in SCI have a high incidence malunion, delayed union, or nonunion and are best treated by internal fixation. HO occurs in 11% of TBI patients, with the hip, shoulder, and elbow being common sites. Trauma dramatically increases the incidence of HO. In SCI, the incidence of HO is 20%, with most occurring in the hip region. A genetic predisposition to form HO is suspected but not proven.

To assess the value of intraoperative arthrography, 48 preoperative hip arthrograms of 35 children under 18 months of age treated for congenital dysplasia of the hip were reviewed. The frequency of the common arthrographic observations was assessed and was compared with the findings observed from the plain roentgenograms, and with the pathoanatomy seen at the time of open reduction. Arthrography proved reliable in identifying the depth of reduction (medial dye column, 100%), the configuration of the osteocartilaginous structures (96%), and the presence of potentially obstructing soft tissue (limbus, 98%, and ligamentum teres, 78%). Arthrography was less reliable in discerning psoas contracture (36%), despite its presence at all open reductions. Arthrography proved reliable in outlining the inverted limbus that can obstruct closed reduction. Because ossification of the femoral head was frequently eccentric, the center edge (CE) angle of Wiberg was calculated from arthrography more accurately than from roentgenograms.

Heterotopic ossification of the shoulder following head injury is a rare occurrence. In a 26-year-old woman with a head injury and extraarticular ossification of the glenohumeral joint, the heterotopic bone was resected surgically when the mass had matured. A vigorous physical therapy program was instituted early after operation to maintain shoulder mobility. Despite the formation of adhesions, the partial reformation of heterotopic bone, and an axillary neuropraxia, the patient achieved an excellent range of active shoulder motion ten months after operation.

Heterotopic ossification is a well-recognized complication of total hip arthroplasty. In a retrospective survey of 98 total hip arthroplasties in ankylosing spondylitis performed between 1970 and 1977, 39.8% showed some evidences of heterotopic ossification. Restriction of hip movements was noted in only two. Heterotopic ossification occurred within one year and was higher (64.6%) in patients with bilateral hip replacements if there was evidence of heterotopic bone formation in one hip. The complications were relatively high in hips with previous operations (55%); trochanteric bursitis (50%); and trochanteric detachment (63.3%). No correlation was found between high erythrocyte sedimentation rate and the incidence or extent of heterotopic bone formation.

This is a report of three children with tender painful patellae, bipartite at the superior, lateral pole. Non-operative treatment failed to relieve these symptoms, but excision of the accessory ossification center resulted in a painless knee. Gross and microscopic pathological examination was consistent with the hypothesis that this syndrome was caused by fracture through the interposed cartilage which failed to heal satisfactorily.

The early and late roentgenograms of the first 100 consecutive Charnley low friction arthroplasties, performed at the Hospital for Special Surgery from October 1968 to October 1970 demonstrate interesting reactions of joint structure. Osteoporosis, early breakage of the wires and trochanteric bed covered by cement were the main factors preventing or delaying the healing of the osteotomy of the greater trochanter. Almost all hips showed a radiolucent line at the acetabular bone-cement junction and about half at the femoral junction. One-third of the hips had increased femoral cortical thickness. Four hips had sterile loosening of the femoral component with a varus shift. Though about one-third of the hips had some ectopic ossification, in only 3 hips was it severe enough to adversely affect the end result. The use of radiopaque cement seems advantageous over the radiolucent type. Arthrography has proven useful for the diagnosis of complications, particularly if subtraction technique is employed.

Periarticular heterotopic ossification (PHO) is a common roentgenographic finding, occurring in more than two-thirds of patients after total hip arthroplasty (THA) for coxarthrosis. In the present study, 56 patients treated with bilateral THA were analyzed to determine the correlation between heterotopic ossification on the two sides. A strong correlation was found between the grade of PHO on the two sides: patients who developed severe PHO after the first THA invariably developed considerable PHO after surgery on the other side. The incidence and grade of PHO were higher in men than in women.