Heterotopic Ossification

Heterotopic Ossification



Heterotopic ossification (HO) has been reported following total hip, knee, cervical arthroplasty, and lumbar arthroplasty, as well as following posterolateral lumbar fusion using recombinant human morphogenetic protein 2 (rhBMP-2).

Heterotopic ossification occurs in three-fourths of the patients after anterior cervical disc arthroplasty at two years after surgery, but does not necessarily correspond to clinical outcome, nor loss or preservation of ROM. The McAfee-Mehren classification should be combined with ROM evaluation to properly study HO 1).

Data regarding HO following anterior cervical discectomy and fusion (ACDF) with rhBMP-2 are sparse. A subanalysis was done of the prospective, multicenter, investigational device exemption trial that compared rhBMP-2 on an absorbable collagen sponge (ACS) versus allograft in ACDF for patients with symptomatic single-level cervical degenerative disc disease.

To assess differences in types of HO observed in the treatment groups and effects of HO on functional and efficacy outcomes, clinical outcomes from previous disc replacement studies were compared between patients who received rhBMP-2/ACS versus allograft. Rate, location, grade, and size of ossifications were assessed preoperatively and at 24 months, and correlated with clinical outcomes. RESULTS Heterotopic ossification was primarily anterior in both groups. Preoperatively in both groups, and including osteophytes in the target regions, HO rates were high at 40.9% and 36.9% for the rhBMP-2/ACS and allograft groups, respectively (p = 0.350). At 24 months, the rate of HO in the rhBMP-2/ACS group was higher than in the allograft group (78.6% vs 59.2%, respectively; p < 0.001). At 24 months, the rate of superior-anterior adjacent-level Park Grade 3 HO was 4.2% in both groups, whereas the rate of Park Grade 2 HO was 19.0% in the rhBMP-2/ACS group compared with 9.8% in the allograft group. At 24 months, the rate of inferior-anterior adjacent-level Park Grade 2/3 HO was 11.9% in the rhBMP-2/ACS group compared with 5.9% in the allograft group. At 24 months, HO rates at the target implant level were similar (p = 0.963). At 24 months, the mean length and anteroposterior diameter of HO were significantly greater in the rhBMP-2/ACS group compared with the allograft group (p = 0.033 and 0.012, respectively). Regarding clinical correlation, at 24 months in both groups, Park Grade 3 HO at superior adjacent-level disc spaces significantly reduced range of motion, more so in the rhBMP-2/ACS group. At 24 months, HO negatively affected Neck Disability Index scores (excluding neck/arm pain scores), neurological status, and overall success in patients in the rhBMP-2/ACS group, but not in patients in the allograft group.

Implantation of rhBMP-2/ACS at 1.5 mg/ml with polyetheretherketone spacer and titanium plate is effective in inducing fusion and improving pain and function in patients undergoing ACDF for symptomatic single-level cervical degenerative disc disease. At 24 months, the rate and dimensions (length and anteroposterior diameter) of HO were higher in the rhBMP-2/ACS group. At 24 months, range of motion was reduced, with Park Grade 3 HO in both treatment groups. The impact of Park Grades 2 and 3 HO on Neck Disability Index success, neurological status, and overall success was not consistent among the treatment groups. The study data may offer a deeper understanding of HO after ACDF and may pave the way for improved device designs 2).


Heterotopic ossification around the hip is a cause of sciatica 3).

Case series

Case reports



Yang X, Bartels RHMA, Donk R, Depreitere B, Walraevens J, Zhai Z, Vleggeert-Lankamp CLA. Does Heterotopic Ossification in Cervical Arthroplasty Affect Clinical Outcome? World Neurosurg. 2019 Jul 31. pii: S1878-8750(19)32103-5. doi: 10.1016/j.wneu.2019.07.187. [Epub ahead of print] PubMed PMID: 31376560.

Arnold PM, Anderson KK, Selim A, Dryer RF, Kenneth Burkus J. Heterotopic ossification following single-level anterior cervical discectomy and fusion: results from the prospective, multicenter, historically controlled trial comparing allograft to an optimized dose of rhBMP-2. J Neurosurg Spine. 2016 Sep;25(3):292-302. doi: 10.3171/2016.1.SPINE15798. Epub 2016 Apr 29. PubMed PMID: 27129045.

Thakkar DH, Porter RW. Heterotopic Ossification Enveloping the Sciatic Nerve Following Posterior Fracture-Dislocation of the Hip: A Case Report. Injury. 1981; 13:207–209

Transsphenoidal approach complications

Transsphenoidal approach complications

No significant differences in surgical outcomes, mortality during the perioperative period or complications were observed between patients younger than 14 years old and similar patients in the general population 1).

Microsurgical and endoscopic techniques are commonly utilized surgical approaches to pituitary pathologies. There are limited data comparing these 2 procedures.

To evaluate postoperative complications, associated costs, and national and regional trends of microscopic and endoscopic techniques in the United States employing a nationwide database.

The Truven MarketScan database 2010 to 2014 was queried and Current Procedural Terminology codes identified patients that underwent microscopic and/or endoscopic transsphenoidal pituitary surgery. International Classification of Diseases codes identified postoperative complications. Adjusted logistic regression and matched propensity analysis evaluated independent odds for complications.

Among 5886 cases studied, 54.49% were microscopic and 45.51% endoscopic. The commonest surgical indications were benign pituitary tumors. Annual trends showed increasing utilization of endoscopic techniques vs microscopic procedures. Postoperative complications occurred in 40.04% of cases, including diabetes insipidus (DI; 16.90%), syndrome of inappropriate antidiuretic hormone (SIADH; 2.02%), iatrogenic hypopituitarism (1.36%), fluid/electrolyte abnormalities (hypoosmolality/hyponatraemia [5.03%] and hyperosmolality/hypernatraemia [2.48%]), and cerebrospinal fluid (CSF) leaks (CSF rhinorrhoea [4.42%] and other CSF leak [6.52%]). In our propensity-based model, patients that underwent endoscopic surgery were more likely to develop DI (odds ratio [OR] = 1.48; 95% confidence interval [CI] = 1.28-1.72), SIADH (OR = 1.53; 95% CI = 1.04-2.24), hypoosmolality/hyponatraemia (OR = 1.17; 95% CI = 1.01-1.34), CSF rhinorrhoea (OR = 2.48; 95% CI = 1.88-3.28), other CSF leak (OR = 1.59; 95% CI = 1.28-1.98), altered mental status (OR = 1.46; 95% CI = 1.01-2.60), and postoperative fever (OR = 4.31; 95% CI = 1.14-16.23). There were no differences in hemorrhagic complications, ophthalmological complications, or bacterial meningitis. Postoperative complications resulted in longer hospitalization and increased healthcare costs.

Endoscopic approaches are increasingly being utilized to manage sellar pathologies relative to microsurgery. Postoperative complications occur in both techniques with higher incidences observed following endoscopic procedures 2).

Internal carotid artery injury

Internal carotid artery injury is a potentially lethal complication in transsphenoidal approach for pituitary lesions. The intercarotid distance (ICD) is thus a major parameter, determining the width of the surgical corridor.

Cerebrospinal fluid leak after endoscopic skull base surgery

Endoscopic transnasal surgery for tumors located at the base of the skull has a high incidence of postoperative cerebrospinal fluid leaks.

see Cerebrospinal fluid leak after endoscopic skull base surgery

Transnasal transsphenoidal (TNTS) resection of pituitary tumors involves wide fluctuation in hemodynamic parameter and causes hypertension and tachycardia due to intense noxious stimuli during various stages of surgery. None of routinely used anesthetic agents effectively blunts the undesirable hemodynamic responses, and therefore usually there is a need to use increased doses of anesthetic agents. Dexmedetomidine may ensure optimal intraoperative hemodynamic stability during critical moments of surgical manipulation. In addition, DEX reduced the anesthetic requirement with rapid recovery at the end of surgery.

DEX as an anesthetic adjuvant improved hemodynamic stability and decreased anesthetic requirements in patients undergoing Transsphenoidal resection of pituitary tumor. In addition, DEX provided better surgical field exposure conditions and early recovery from anesthesia 3).

Sinonasal complications

A high incidence of nasal complications after conventional transsphenoidal surgery observed through examination and not reported spontaneously point to the need of otorhinolaryngological investigation complemented by nasal endoscopy in patients submitted to procedures through this route4)

Olfactory dysfunction

The patients must be informed that their olfaction may be impaired 5).


The percentage of nasal obstruction and nasal crusting was 38% in Monnier’s series evaluating the transvestibular transeptal approach 6).

Chronic nasal irritation was seen in only 2% of cases in Feigenbaun et al.’s series 7).

A study assessed the long-term impact of endoscopic skull base surgery on olfaction, sinonasal symptoms, mucociliary clearance time (MCT), and quality of life (QoL). Patients with pituitary adenomas underwent TTEA (n = 38), while patients with other benign parasellar tumours who underwent an EEA with vascularised nasoseptal flap reconstruction (n = 17) were enrolled in this prospective study between 2009 and 2012. Sinonasal symptoms (Visual Analogue Scale), subjective olfactometry (Barcelona Smell Test-24, BAST-24), MCT (saccharin test), and QoL (short form SF-36, rhinosinusitis outcome measure/RSOM) were evaluated before, and 12 months after, surgery. At baseline, sinonasal symptoms, MCT, BAST-24, and QoL were similar between groups. Twelve months after surgery, both TTEA and EEA groups experienced smell impairment compared to baseline. Moreover, EEA (but not TTEA) patients reported increased posterior nasal discharge and longer MCTs compared to baseline. No significant changes in olfactometry or QoL were detected in either group 12 months after surgery. Over the long-term, expanded skull base surgery, using EEA, produced more sinonasal symptoms (including loss of smell) and longer MCTs than pituitary surgery (TTEA). EEA showed no long-term impact on smell test or QoL 8).

Hyponatremia after transsphenoidal surgery



Zhao Y, Lian W, Xing B, Wang R. The characteristics of and surgical treatment for pituitary adenomas in patients under 14 years old. Clin Neurol Neurosurg. 2019 Jul 12;184:105423. doi: 10.1016/j.clineuro.2019.105423. [Epub ahead of print] Review. PubMed PMID: 31376772.

Asemota AO, Ishii M, Brem H, Gallia GL. Comparison of Complications, Trends, and Costs in Endoscopic vs Microscopic Pituitary Surgery: Analysis From a US Health Claims Database. Neurosurgery. 2017 Sep 1;81(3):458-472. doi: 10.1093/neuros/nyx350. PubMed PMID: 28859453.

Gopalakrishna KN, Dash PK, Chatterjee N, Easwer HV, Ganesamoorthi A. Dexmedetomidine as an Anesthetic Adjuvant in Patients Undergoing Transsphenoidal Resection of Pituitary Tumor. J Neurosurg Anesthesiol. 2014 Dec 9. [Epub ahead of print] PubMed PMID: 25493927.

Petry C, Leães CG, Pereira-Lima JF, Gerhardt KD, Sant GD, Oliveira Mda C. Oronasal complications in patients after transsphenoidal hypophyseal surgery. Braz J Otorhinolaryngol. 2009 May-Jun;75(3):345-9. English, Portuguese. PubMed PMID: 19649482.

Kim BY, Kang SG, Kim SW, Hong YK, Jeun SS, Kim SW, Kim HB, Kim M, Maeng JH, Lee DC, Cho JH, Park YJ. Olfactory changes after endoscopic endonasal transsphenoidal approach for skull base tumors. Laryngoscope. 2014 Mar 13. doi: 10.1002/lary.24674. [Epub ahead of print] PubMed PMID: 24623575.

Monnier DS. Séquelles endonasales après hypophysectomie. Ann Otolaryngol Chir Cervicofac. 1998;115:49-53.

Feigenbaum SL, Downey DE, Wilson CB, Jaffe RB. Transsphenoidal pituitary resection for preoperative diagnosis of prolactin-secreing pituitary adenoma in women: long term follow-up. J Clin Endocrinol Metab. 1996;81(5):1711-19

Rioja E, Bernal-Sprekelsen M, Enriquez K, Enseñat J, Valero R, de Notaris M, Mullol J, Alobid I. Long-term outcomes of endoscopic endonasal approach for skull base surgery: a prospective study. Eur Arch Otorhinolaryngol. 2016 Jul;273(7):1809-17. doi: 10.1007/s00405-015-3853-9. Epub 2015 Dec 19. PubMed PMID: 26688432.

Tandem spinal stenosis

Tandem spinal stenosis

Tandem spinal stenosis (TSS) is a degenerative spinal condition characterized by spinal canal narrowing at 2 or more distinct spinal levels. It is an aging-related condition that is likely to increase as the population ages, but which remains poorly described in the literature.

It is a common condition present in up to 60% of patients with spinal stenosis. This disorder, however, is often overlooked, which can lead to serious complications. Identification of tandem spinal stenosis is paramount as a first step in management and, although there is still no preferred intervention, both staged and simultaneous procedures have been shown to be effective. Surgeons may utilize a single, staged, or combined approach to decompression, always addressing cervical myelopathy as a priority 1).

The purpose of a study of van Eck et al. was to develop a simple and clinically useful morphological classification system for congenital lumbar spinal stenosis using sagittal MRI, allowing clinicians to recognize patterns of lumbar congenital stenosis quickly and be able to screen these patients for tandem cervical stenosis.

Forty-four subjects with an MRI of both the cervical and lumbar spine were included. On the lumbar spine MRI, the sagittal canal morphology was classified as one of three types: Type I normal, Type II partially narrow, Type III globally narrow. For the cervical spine, the Torg-Pavlov ratio on X-ray and the cervical spinal canal width on MRI were measured. Kruskal-Wallis analysis was done to determine if there was a relationship between the sagittal morphology of the lumbar spinal canal and the presence of cervical spinal stenosis.

Subjects with a type III globally narrow lumbar spinal canal had a significantly lower cervical Torg-Pavlov ratio and smaller cervical spinal canal width than those with a type I normal lumbar spinal canal.

A type III lumbar spinal canal is a globally narrow canal characterized by a lack of spinal fluid around the conus. This was defined as “functional lumbar spinal stenosis” and is associated with an increased incidence of tandem cervical spinal stenosis 2).

Pennington et al. sought to determine the impact of primary lumbar decompression on quality of life (QOL) outcomes in patients with symptomatic TSS.

They retrospectively reviewed 803 patients with clinical and radiographic evidence of TSS treated between 2008 and 2014 with a minimum 2-year follow-up. The records of patients with clinical and radiographic evidence of concurrent cervical and lumbar stenosis were reviewed. Prospectively gathered QOL data, including the Pain Disability Questionnaire (PDQ), Patient Health Questionnaire-9 (PHQ-9), EuroQOL-5 Dimensions (EQ-5D), and Visual Analogue Scale (VAS) for low back pain, were assessed at the 6-month, 1-year, and 2-year follow-ups.

Of 803 identified patients (mean age 66.2 years; 46.9% male), 19.6% underwent lumbar decompression only, 14.1% underwent cervical + lumbar decompression, and 66.4% underwent conservative management only. Baseline VAS scores were similar across all groups, but patients undergoing conservative management had better baseline QOL scores on all other measures. Both surgical cohorts experienced significant improvements in the VAS, PDQ, and EQ-5D at all time points; patients in the cervical + lumbar cohort also had significant improvement in the PHQ-9. Conservatively managed patients showed no significant improvement in QOL scores at any follow-up interval.

Lumbar decompression with or without cervical decompression improves low back pain and QOL outcomes in patients with TSS. The decision to prioritize lumbar decompression is therefore unlikely to adversely affect long-term quality-of-life improvements 3).

Cervical spine surgery with or without follow-up lumbar spine surgery significantly improves neck pain in patients with TSS. In contrast, cervical spine surgery in these patients does not improve lumbar symptoms. Lumbar spine surgery also did not improve low back pain or quality of life. Future prospective studies are necessary to examine the impact of lumbar decompression alone on cervical spine symptoms in patients with TSS4).



Overley SC, Kim JS, Gogel BA, Merrill RK, Hecht AC. Tandem Spinal Stenosis: A Systematic Review. JBJS Rev. 2017 Sep;5(9):e2. doi: 10.2106/JBJS.RVW.17.00007. Review. PubMed PMID: 28872572.

van Eck CF, Spina Iii NT, Lee JY. A novel MRI classification system for congenital functional lumbar spinal stenosis predicts the risk for tandem cervical spinal stenosis. Eur Spine J. 2017 Feb;26(2):368-373. doi: 10.1007/s00586-016-4657-3. Epub 2016 Jun 20. PubMed PMID: 27323965.

Pennington Z, Alentado VJ, Lubelski D, Alvin MD, Levin JM, Benzel EC, Mroz TE. Quality of life changes after lumbar decompression in patients with tandem spinal stenosis. Clin Neurol Neurosurg. 2019 Jul 26;184:105455. doi: 10.1016/j.clineuro.2019.105455. [Epub ahead of print] PubMed PMID: 31376775.

Alvin MD, Alentado VJ, Lubelski D, Benzel EC, Mroz TE. Cervical spine surgery for tandem spinal stenosis: The impact on low back pain. Clin Neurol Neurosurg. 2018 Mar;166:50-53. doi: 10.1016/j.clineuro.2018.01.024. PubMed PMID: 29408772.
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